Detecting Object(s) Within a Radius

Hello, and thanks for reading. I'm new to Arduino, but not coding. I have a decent understanding of electronics in general, but I don't know how to accomplish the following:

I'd like an Arduino to detect unique devices at a range of approximately 5 meters, +/- 1 meter.

When device A is the only device present, begin counting time.

When device B is the only device present, begin counting time.

When both devices are present, do not count time.

Is there any hardware with a range this narrow? Or is there a better way to start the counters from a hardware perspective?

Pozyx should do it, link here;

Posyx

srnet:
Pozyx should do it, link here;

Posyx

Amazing! This is perfect for what I'm trying to do. Thanks for your reply.

You must be one of the very few that is not instantly put off by its price tag!

wvmarle:
You must be one of the very few that is not instantly put off by its price tag!

It's a company project. If it can be done in a more inexpensive way, I'd love to hear it. But my manager will have no qualms signing that expense request.

chetlos:
If it can be done in a more inexpensive way, I'd love to hear it.

If it could (reliably) you would expect to be able to buy it cheap on eBay.