I was considering partially disassembling my X-10 wireless webcamera to do the same thing. All I would up doing is strapping the thing to the top of the cab with tape.
The problems you will always face are ones of transmitting power and anetenna orientation. The X-10 has a blade antenna which means that the signal will tend to go out of phase when rounding corners. My advice is to get the receive antenna as close to the track as possible (center of the layout if you can) and use and omni broadcast antenna.
Hopefully, you can then see without too much image break up. I’ve put a view example on my train page: www.y2kfam.com/railroad.htm Perhaps it will help? By please let me know how you’re progressing!