Put a D1-Mini style ESP8266 into one side with hole for USB cable and an HC-SR501 PIR Motion Sensor in the other side. And another hole to feed additional IO wires. Some tabs to help alignment but will require some sort of adhesive to join the parts.

My first print. Everything seems just a little smaller than expected so the motion sensor is a very tight fit. Maybe a little sanding will fix this. The tabs are a bit weak and there could be some supports for the ESP board to sit level in place.

note: includes the name ‘Leon’ embossed in the motion sensor face.