diff --git a/homeassistant/components/mobile_app/const.py b/homeassistant/components/mobile_app/const.py
index 31364ba063da..05d240da909d 100644
--- a/homeassistant/components/mobile_app/const.py
+++ b/homeassistant/components/mobile_app/const.py
@@ -171,7 +171,7 @@ REGISTER_SENSOR_SCHEMA = vol.Schema({
     vol.Required(ATTR_SENSOR_NAME): cv.string,
     vol.Required(ATTR_SENSOR_TYPE): vol.In(SENSOR_TYPES),
     vol.Required(ATTR_SENSOR_UNIQUE_ID): cv.string,
-    vol.Required(ATTR_SENSOR_UOM): cv.string,
+    vol.Optional(ATTR_SENSOR_UOM): cv.string,
     vol.Required(ATTR_SENSOR_STATE): vol.Any(bool, str, int, float),
     vol.Optional(ATTR_SENSOR_ICON, default='mdi:cellphone'): cv.icon,
 })
diff --git a/homeassistant/components/mobile_app/sensor.py b/homeassistant/components/mobile_app/sensor.py
index c6a53ce57ec7..b2846a6002b1 100644
--- a/homeassistant/components/mobile_app/sensor.py
+++ b/homeassistant/components/mobile_app/sensor.py
@@ -55,4 +55,4 @@ class MobileAppSensor(MobileAppEntity):
     @property
     def unit_of_measurement(self):
         """Return the unit of measurement this sensor expresses itself in."""
-        return self._config[ATTR_SENSOR_UOM]
+        return self._config.get(ATTR_SENSOR_UOM)
diff --git a/homeassistant/components/mobile_app/webhook.py b/homeassistant/components/mobile_app/webhook.py
index 7a83ba4e978f..28ef6bccd6ad 100644
--- a/homeassistant/components/mobile_app/webhook.py
+++ b/homeassistant/components/mobile_app/webhook.py
@@ -228,7 +228,7 @@ async def handle_webhook(hass: HomeAssistantType, webhook_id: str,
                                                   data[ATTR_SENSOR_TYPE])
         async_dispatcher_send(hass, register_signal, data)
 
-        return webhook_response({"status": "registered"},
+        return webhook_response({'success': True},
                                 registration=registration, status=HTTP_CREATED,
                                 headers=headers)
 
@@ -271,7 +271,7 @@ async def handle_webhook(hass: HomeAssistantType, webhook_id: str,
 
             async_dispatcher_send(hass, SIGNAL_SENSOR_UPDATE, new_state)
 
-            resp[unique_id] = {"status": "okay"}
+            resp[unique_id] = {'success': True}
 
         return webhook_response(resp, registration=registration,
                                 headers=headers)
diff --git a/tests/components/mobile_app/test_entity.py b/tests/components/mobile_app/test_entity.py
index 5dc285cfe9ed..3d8e575f6867 100644
--- a/tests/components/mobile_app/test_entity.py
+++ b/tests/components/mobile_app/test_entity.py
@@ -35,7 +35,7 @@ async def test_sensor(hass, create_registrations, webhook_client):  # noqa: F401
     assert reg_resp.status == 201
 
     json = await reg_resp.json()
-    assert json == {'status': 'registered'}
+    assert json == {'success': True}
 
     entity = hass.states.get('sensor.battery_state')
     assert entity is not None
@@ -122,7 +122,7 @@ async def test_sensor_id_no_dupes(hass, create_registrations,  # noqa: F401, F81
     assert reg_resp.status == 201
 
     reg_json = await reg_resp.json()
-    assert reg_json == {'status': 'registered'}
+    assert reg_json == {'success': True}
 
     dupe_resp = await webhook_client.post(webhook_url, json=payload)