There are commercial systems that will do what the OP wants, but not for anything like $300.
GE make a system called Locotrol which is for controlling locomotives at both ends of a train via radio.
Has to be insanely reliable, but the radios are very expensive, but cheap when you consider what a locomotive costs.
http://www.getransportation.com/railconnect360/locotrol-distributed-power-systems