ST presence sensor replacement

I know that there is a love/hate relationship with these, however I used them for various projects. Since they are discontinued and it seems sold out everywhere, what options do I have left? I need presence detection that can run off of 12vdc. Nothing cloud, phone, or GPS based.

Any thougts?

An Xbee3 can be programmed as an arrival sensor and works even better than the SmartThings arrival sensor.
The Xbee3 pro has much better range.

I have seen this mentioned a few times. But haven't been able to find a good write up on how to do this. I have zero experience with Xbee but willing to learn if someone can point me to what I need to do.