Single RF transmitter receiver pair

Hi, I am a novice interested in building a RF transmitter receiver pair.

The transmitter would need to single when a variable resister goes low (or high?). The receiver would go high and switch on a low voltage LED light.

Can this be done with a simple pressure sensor resister on the transmitter side and a LED on the receiver side?

I need the receiver be small and light enough to fit on a kid's helmet. Some friend suggested using a Arduino Uno but they are cumbersome. Isn't it possible to build a single purpose "switch" with a FR pair?

Thanks