Basically, any sort of circuitry creates the harmonic that a Recco picks up. However, actual Recco tags give a much larger signal, so they're way easier to find.
Because it's not much circuitry, a Gopro is a little difficult. That said, it can and has been done. Some of you might remember that we found mine in Grace Lakes last year.
The largest question is how much is going on for patrol, and what sort of time they have to do a proper search with the Recco. Obviously, they can't drop what they're doing every time someone loses a phone or camera.
I'll do what I can.
Big takeaway: glue a Recco reflector onto your important gear. Super easy to find.