I am a young inventor(one patent) researching for a proof of concept protect. I need an RC transmitter/receiver set with the following: small receiver, cheap, able to close a simple circuit, multiple could function independently but very close together, not very delicate. I don't need it to do multiple functions; a single push button is best. I want to buy, but if it is easy to build, and still meets specs, that would work too.

 

A garage door opener controller/xmitter.

 

A garage door opener controller/xmitter.

thanks! i will do some more snooping around before i buy anything, but this looks good

 

If small size receiver is a priority then look at model aeroplane radio control.
Building it from scratch isn't too difficult, but depending where you are in the world there are rules about transmitters to avoid interfering with other things which can be difficult to meet and to know whether your design does meet those rules.