What hardware should I buy if I want to get started with embedded in Rust?

The software side, I can figure out probably.

I just want to know what the "starter pack" would be for embedded development, and where would I get extra parts / new boards etc.

A project I was thinking of making was a little device that connects to my home wifi and sends a notification to my phone whenever a proximity sensor is triggered.

My kids forget to lock the latch on the back door all the time so I want to place the proximity sensor so that it will see the latch when it's locked, but when it's unlocked it will be too far away to see it, and thus let me know when the boys leave the door unlocked.