diff --git a/habitat-hitl/habitat_hitl/core/client_message_manager.py b/habitat-hitl/habitat_hitl/core/client_message_manager.py
index 3daddd3c8c..2a84716587 100644
--- a/habitat-hitl/habitat_hitl/core/client_message_manager.py
+++ b/habitat-hitl/habitat_hitl/core/client_message_manager.py
@@ -4,6 +4,7 @@
 # This source code is licensed under the MIT license found in the
 # LICENSE file in the root directory of this source tree.
 
+from dataclasses import dataclass
 from typing import Final, List, Optional, Union
 
 import magnum as mn
@@ -14,6 +15,19 @@
 DEFAULT_NORMAL: Final[List[float]] = [0.0, 1.0, 0.0]
 
 
+# TODO: Move to another file.
+@dataclass
+class UIButton:
+    """
+    Networked UI button. Use RemoteClientState.ui_button_pressed() to retrieve state.
+    """
+
+    def __init__(self, button_id: str, text: str, enabled: bool):
+        self.button_id = button_id
+        self.text = text
+        self.enabled = enabled
+
+
 class ClientMessageManager:
     r"""
     Extends gfx-replay keyframes to include server messages to be interpreted by the clients.
@@ -144,6 +158,34 @@ def add_text(
                 {"text": text, "position": [pos[0], pos[1]]}
             )
 
+    def show_modal_dialogue_box(
+        self,
+        title: str,
+        text: str,
+        buttons: List[UIButton],
+        destination_mask: Mask = Mask.ALL,
+    ):
+        r"""
+        Show a modal dialog box with buttons.
+        There can only be one modal dialog box at a time.
+        """
+        for user_index in self._users.indices(destination_mask):
+            message = self._messages[user_index]
+
+            message["dialog"] = {
+                "title": title,
+                "text": text,
+                "buttons": [],
+            }
+            for button in buttons:
+                message["dialog"]["buttons"].append(
+                    {
+                        "id": button.button_id,
+                        "text": button.text,
+                        "enabled": button.enabled,
+                    }
+                )
+
     def change_humanoid_position(
         self, pos: List[float], destination_mask: Mask = Mask.ALL
     ) -> None:
diff --git a/habitat-hitl/habitat_hitl/core/remote_client_state.py b/habitat-hitl/habitat_hitl/core/remote_client_state.py
index d32cdc9ee0..97ace70907 100644
--- a/habitat-hitl/habitat_hitl/core/remote_client_state.py
+++ b/habitat-hitl/habitat_hitl/core/remote_client_state.py
@@ -5,7 +5,7 @@
 # LICENSE file in the root directory of this source tree.
 
 import math
-from typing import Any, List, Optional, Tuple
+from typing import Any, List, Optional, Set, Tuple
 
 import magnum as mn
 
@@ -49,6 +49,9 @@ def __init__(
         self._on_client_connected = Event()
         self._on_client_disconnected = Event()
 
+        # TODO: Handle UI in a different class.
+        self._pressed_ui_buttons: List[Set[str]] = []
+
         self._gui_inputs: List[GuiInput] = []
         self._client_state_history: List[List[ClientState]] = []
         self._receive_rate_trackers: List[AverageRateTracker] = []
@@ -56,6 +59,7 @@ def __init__(
             self._gui_inputs.append(GuiInput())
             self._client_state_history.append([])
             self._receive_rate_trackers.append(AverageRateTracker(2.0))
+            self._pressed_ui_buttons.append(set())
 
         # temp map VR button to key
         self._button_map = {
@@ -89,6 +93,9 @@ def bind_gui_input(self, gui_input: GuiInput, user_index: int) -> None:
         assert user_index < len(self._gui_inputs)
         self._gui_inputs[user_index] = gui_input
 
+    def ui_button_pressed(self, user_index: int, button_id: str) -> bool:
+        return button_id in self._pressed_ui_buttons[user_index]
+
     def get_history_length(self) -> int:
         """Length of client state history preserved. Anything beyond this horizon is discarded."""
         return 4
@@ -211,13 +218,19 @@ def _update_input_state(
         if len(all_client_states) == 0 or len(self._gui_inputs) == 0:
             return
 
-        # Gather all recent keyDown and keyUp events
+        # Gather all input events.
         for user_index in range(len(all_client_states)):
             client_states = all_client_states[user_index]
             if len(client_states) == 0:
                 continue
             gui_input = self._gui_inputs[user_index]
             for client_state in client_states:
+                # UI element events.
+                ui = client_state.get("ui", None)
+                if ui is not None:
+                    for button in ui.get("buttonsPressed", []):
+                        self._pressed_ui_buttons[user_index].add(button)
+
                 input_json = (
                     client_state["input"] if "input" in client_state else None
                 )
@@ -447,11 +460,13 @@ def get_new_connection_records(self) -> List[ConnectionRecord]:
     def on_frame_end(self) -> None:
         for user_index in self._users.indices(Mask.ALL):
             self._gui_inputs[user_index].on_frame_end()
+            self._pressed_ui_buttons[user_index].clear()
         self._new_connection_records = None
 
     def clear_history(self, user_mask=Mask.ALL) -> None:
         for user_index in self._users.indices(user_mask):
             self._client_state_history[user_index].clear()
+            self._pressed_ui_buttons[user_index].clear()
 
     def kick(self, user_mask: Mask) -> None:
         """