I have just made and testing a version of the station stop board to fit inside of a Garden railway loco and it uses a reed switch under the loco. 2 magnets, 1 on each end of the track where the loco is to stop.
Still testing and when happy with it i will get some board made.
All my stuff is for sale on EBay at the moment. But will be here soon.
Regards Andy Quirot