That old Android phone in your drawer is a full sensor platform. It packs a camera, microphone, light sensor, barometer, accelerometer, proximity sensor, and a touchscreen, all on your WiFi. So don’t recycle it. You can turn it into a motion-detecting security camera, a room sensor that posts data over MQTT, or a wall-mounted Home Assistant dashboard. That dashboard rivals commercial smart displays costing $150 or more. The whole setup runs on free software, keeps your data local, and takes about an hour.