Sensors

DeviceQuantityConnectionIntegrationNotes
Nest Protect v2 Battery3Wi-FiNestDual Smoke and CO Alarm. One of the best fire/carbon monoxide alarms. But recently Google has removed API access, and so the integration with Home Assistant is no longer working.
Aqara Vibration Sensor2ZigbeeBinary SensorI purchased it to automate (getting end of the cycle notificatoins) from my washing machine and dryer. Not reliably automated yet.

I wrote a script to blink Philips Hue bulbs when there is an alarm from Nest Protect. Now that the Nest integration is broken, this has become useless.