[apienx]

The quick and dirty method is to point your phone at the suspicious device in total darkness. A modern smartphone will pick up the infrared (your eyes won't). Or get yourself a simple RF detector (or even a Software Defined Radio).

You might find this presentation useful (!PDF!). https://defcon.org/images/defcon-22/dc-22-presentations/Pols...

Privacy is a human right. Best of luck!