diff --git a/cartographer/mapping/map_builder_test.cc b/cartographer/mapping/map_builder_test.cc
index 4ecf6f2..0b0a754 100644
--- a/cartographer/mapping/map_builder_test.cc
+++ b/cartographer/mapping/map_builder_test.cc
@@ -121,7 +121,7 @@ TEST_F(MapBuilderTest, TrajectoryAddFinish2D) {
   const std::unordered_set<std::string> expected_sensor_ids = {kRangeSensorId};
   int trajectory_id = map_builder_->AddTrajectoryBuilder(
       expected_sensor_ids, trajectory_builder_options_,
-      nullptr /* local_slam_result_callback */);
+      nullptr /* GetLocalSlamResultCallbackForSubscriptions */);
   EXPECT_EQ(1, map_builder_->num_trajectory_builders());
   EXPECT_TRUE(map_builder_->GetTrajectoryBuilder(trajectory_id) != nullptr);
   EXPECT_TRUE(map_builder_->pose_graph() != nullptr);
@@ -136,7 +136,7 @@ TEST_F(MapBuilderTest, TrajectoryAddFinish3D) {
   const std::unordered_set<std::string> expected_sensor_ids = {kRangeSensorId};
   int trajectory_id = map_builder_->AddTrajectoryBuilder(
       expected_sensor_ids, trajectory_builder_options_,
-      nullptr /* local_slam_result_callback */);
+      nullptr /* GetLocalSlamResultCallbackForSubscriptions */);
   EXPECT_EQ(1, map_builder_->num_trajectory_builders());
   EXPECT_TRUE(map_builder_->GetTrajectoryBuilder(trajectory_id) != nullptr);
   EXPECT_TRUE(map_builder_->pose_graph() != nullptr);
diff --git a/cartographer_grpc/handlers/add_trajectory_handler.h b/cartographer_grpc/handlers/add_trajectory_handler.h
index fb25fd4..f90a388 100644
--- a/cartographer_grpc/handlers/add_trajectory_handler.h
+++ b/cartographer_grpc/handlers/add_trajectory_handler.h
@@ -30,6 +30,9 @@ class AddTrajectoryHandler
                                    proto::AddTrajectoryResponse> {
  public:
   void OnRequest(const proto::AddTrajectoryRequest& request) override {
+    auto local_slam_result_callback =
+        GetUnsynchronizedContext<MapBuilderServer::MapBuilderContext>()
+            ->GetLocalSlamResultCallbackForSubscriptions();
     const int trajectory_id =
         GetContext<MapBuilderServer::MapBuilderContext>()
             ->map_builder()
@@ -37,7 +40,7 @@ class AddTrajectoryHandler
                                       request.expected_sensor_ids().begin(),
                                       request.expected_sensor_ids().end()),
                                   request.trajectory_builder_options(),
-                                  nullptr /* local_slam_result_callback */);
+                                  local_slam_result_callback);
     auto response =
         cartographer::common::make_unique<proto::AddTrajectoryResponse>();
     response->set_trajectory_id(trajectory_id);
diff --git a/cartographer_grpc/map_builder_server.cc b/cartographer_grpc/map_builder_server.cc
index 73a8c28..d30c962 100644
--- a/cartographer_grpc/map_builder_server.cc
+++ b/cartographer_grpc/map_builder_server.cc
@@ -34,26 +34,40 @@ const cartographer::common::Duration kPopTimeout =
 }  // namespace
 
 MapBuilderServer::MapBuilderContext::MapBuilderContext(
-    cartographer::mapping::MapBuilder* map_builder,
-    cartographer::common::BlockingQueue<std::unique_ptr<SensorData>>*
-        sensor_data_queue)
-    : map_builder_(map_builder), sensor_data_queue_(sensor_data_queue) {}
+    MapBuilderServer* map_builder_server)
+    : map_builder_server_(map_builder_server) {}
 
 cartographer::mapping::MapBuilder&
 MapBuilderServer::MapBuilderContext::map_builder() {
-  return *map_builder_;
+  return map_builder_server_->map_builder_;
 }
 
 cartographer::common::BlockingQueue<
     std::unique_ptr<MapBuilderServer::SensorData>>&
 MapBuilderServer::MapBuilderContext::sensor_data_queue() {
-  return *sensor_data_queue_;
+  return map_builder_server_->sensor_data_queue_;
+}
+
+cartographer::mapping::TrajectoryBuilderInterface::LocalSlamResultCallback
+MapBuilderServer::MapBuilderContext::
+    GetLocalSlamResultCallbackForSubscriptions() {
+  MapBuilderServer* map_builder_server = map_builder_server_;
+  return [map_builder_server](
+             int trajectory_id, cartographer::common::Time time,
+             cartographer::transform::Rigid3d local_pose,
+             cartographer::sensor::RangeData range_data,
+             std::unique_ptr<const cartographer::mapping::NodeId> node_id) {
+    map_builder_server->OnLocalSlamResult(trajectory_id, time, local_pose,
+                                          std::move(range_data),
+                                          std::move(node_id));
+  };
 }
 
 void MapBuilderServer::MapBuilderContext::AddSensorDataToTrajectory(
     const SensorData& sensor_data) {
   sensor_data.sensor_data->AddToTrajectoryBuilder(
-      map_builder_->GetTrajectoryBuilder(sensor_data.trajectory_id));
+      map_builder_server_->map_builder_.GetTrajectoryBuilder(
+          sensor_data.trajectory_id));
 }
 
 MapBuilderServer::MapBuilderServer(
@@ -82,8 +96,7 @@ MapBuilderServer::MapBuilderServer(
                                  proto::MapBuilderService>("FinishTrajectory");
   grpc_server_ = server_builder.Build();
   grpc_server_->SetExecutionContext(
-      cartographer::common::make_unique<MapBuilderContext>(
-          &map_builder_, &sensor_data_queue_));
+      cartographer::common::make_unique<MapBuilderContext>(this));
 }
 
 void MapBuilderServer::Start() {
@@ -127,4 +140,39 @@ void MapBuilderServer::StartSlamThread() {
       [this]() { this->ProcessSensorDataQueue(); });
 }
 
+void MapBuilderServer::OnLocalSlamResult(
+    int trajectory_id, cartographer::common::Time time,
+    cartographer::transform::Rigid3d local_pose,
+    cartographer::sensor::RangeData range_data,
+    std::unique_ptr<const cartographer::mapping::NodeId> node_id) {
+  auto shared_range_data =
+      std::make_shared<cartographer::sensor::RangeData>(std::move(range_data));
+  cartographer::common::MutexLocker locker(&local_slam_subscriptions_lock_);
+  for (auto& entry : local_slam_subscriptions_[trajectory_id]) {
+    auto copy_of_node_id =
+        node_id ? cartographer::common::make_unique<
+                      const cartographer::mapping::NodeId>(*node_id)
+                : nullptr;
+    LocalSlamSubscriptionCallback callback = entry.second;
+    callback(trajectory_id, time, local_pose, shared_range_data,
+             std::move(copy_of_node_id));
+  }
+}
+
+MapBuilderServer::SubscriptionId MapBuilderServer::SubscribeLocalSlamResults(
+    int trajectory_id, LocalSlamSubscriptionCallback callback) {
+  cartographer::common::MutexLocker locker(&local_slam_subscriptions_lock_);
+  local_slam_subscriptions_[trajectory_id].emplace(current_subscription_index_,
+                                                   callback);
+  return SubscriptionId{trajectory_id, current_subscription_index_++};
+}
+
+void MapBuilderServer::UnsubscribeLocalSlamResults(
+    const SubscriptionId& subscription_id) {
+  cartographer::common::MutexLocker locker(&local_slam_subscriptions_lock_);
+  CHECK_EQ(local_slam_subscriptions_[subscription_id.trajectory_id].erase(
+               subscription_id.subscription_index),
+           1u);
+}
+
 }  // namespace cartographer_grpc
diff --git a/cartographer_grpc/map_builder_server.h b/cartographer_grpc/map_builder_server.h
index 573a3f3..2896525 100644
--- a/cartographer_grpc/map_builder_server.h
+++ b/cartographer_grpc/map_builder_server.h
@@ -18,7 +18,9 @@
 #define CARTOGRAPHER_GRPC_MAP_BUILDER_SERVER_H
 
 #include "cartographer/common/blocking_queue.h"
+#include "cartographer/common/time.h"
 #include "cartographer/mapping/map_builder.h"
+#include "cartographer/mapping/trajectory_builder_interface.h"
 #include "cartographer/sensor/data.h"
 #include "cartographer_grpc/framework/execution_context.h"
 #include "cartographer_grpc/framework/server.h"
@@ -28,26 +30,38 @@ namespace cartographer_grpc {
 
 class MapBuilderServer {
  public:
+  using LocalSlamSubscriptionCallback = std::function<void(
+      int /* trajectory ID */, cartographer::common::Time,
+      cartographer::transform::Rigid3d /* local pose estimate */,
+      std::shared_ptr<
+          const cartographer::sensor::RangeData> /* in local frame */,
+      std::unique_ptr<const cartographer::mapping::NodeId>)>;
   struct SensorData {
     int trajectory_id;
     std::unique_ptr<cartographer::sensor::Data> sensor_data;
   };
+  struct SubscriptionId {
+    const int trajectory_id;
+    const int subscription_index;
+  };
 
   class MapBuilderContext : public framework::ExecutionContext {
    public:
-    MapBuilderContext(
-        cartographer::mapping::MapBuilder* map_builder,
-        cartographer::common::BlockingQueue<std::unique_ptr<SensorData>>*
-            sensor_data_queue);
+    MapBuilderContext(MapBuilderServer* map_builder_server);
     cartographer::mapping::MapBuilder& map_builder();
     cartographer::common::BlockingQueue<std::unique_ptr<SensorData>>&
     sensor_data_queue();
+    cartographer::mapping::TrajectoryBuilderInterface::LocalSlamResultCallback
+    GetLocalSlamResultCallbackForSubscriptions();
     void AddSensorDataToTrajectory(const SensorData& sensor_data);
+    SubscriptionId SubscribeLocalSlamResults(
+        int trajectory_id, LocalSlamSubscriptionCallback callback);
+    void UnsubscribeLocalSlamResults(const SubscriptionId& subscription_id);
 
     template <typename SensorDataType>
     void EnqueueSensorData(int trajectory_id, const std::string& sensor_id,
                            const SensorDataType& sensor_data) {
-      sensor_data_queue_->Push(
+      map_builder_server_->sensor_data_queue_.Push(
           cartographer::common::make_unique<MapBuilderServer::SensorData>(
               MapBuilderServer::SensorData{
                   trajectory_id, cartographer::sensor::MakeDispatchable(
@@ -55,10 +69,9 @@ class MapBuilderServer {
     }
 
    private:
-    cartographer::mapping::MapBuilder* map_builder_;
-    cartographer::common::BlockingQueue<std::unique_ptr<SensorData>>*
-        sensor_data_queue_;
+    MapBuilderServer* map_builder_server_;
   };
+  friend MapBuilderContext;
 
   MapBuilderServer(
       const proto::MapBuilderServerOptions& map_builder_server_options);
@@ -75,8 +88,19 @@ class MapBuilderServer {
   void Shutdown();
 
  private:
+  using LocalSlamResultHandlerSubscriptions =
+      std::map<int /* subscription_index */, LocalSlamSubscriptionCallback>;
+
   void ProcessSensorDataQueue();
   void StartSlamThread();
+  void OnLocalSlamResult(
+      int trajectory_id, cartographer::common::Time time,
+      cartographer::transform::Rigid3d local_pose,
+      cartographer::sensor::RangeData range_data,
+      std::unique_ptr<const cartographer::mapping::NodeId> node_id);
+  SubscriptionId SubscribeLocalSlamResults(
+      int trajectory_id, LocalSlamSubscriptionCallback callback);
+  void UnsubscribeLocalSlamResults(const SubscriptionId& subscription_id);
 
   bool shutting_down_ = false;
   std::unique_ptr<std::thread> slam_thread_;
@@ -84,6 +108,10 @@ class MapBuilderServer {
   cartographer::mapping::MapBuilder map_builder_;
   cartographer::common::BlockingQueue<std::unique_ptr<SensorData>>
       sensor_data_queue_;
+  cartographer::common::Mutex local_slam_subscriptions_lock_;
+  int current_subscription_index_ = 0;
+  std::map<int /* trajectory ID */, LocalSlamResultHandlerSubscriptions>
+      local_slam_subscriptions_ GUARDED_BY(local_slam_subscriptions_lock_);
 };
 
 }  // namespace cartographer_grpc