Arduino might be something worth pursuing, if you're handy with such things. A couple people have figured out how to interface arduino's with existing R/C systems, here is one where someone used the trainer input plug on an airplane radio to built a custom interface to arduino:

http://www.arduino.cc/cgi-bin/yabb2/...num=1193927390

Another thought would be to use arduino with the Xbee shield and do a fully custom transmitter / receiver pair, but the range on this wouldn't be all that great (100 ft, 300ft line of sight).

As far as a "Kit", I'm not sure one exists.