If you have lots of RC creations about ... easily scalable to a large number of receivers. The transmitter can be made of anything to hand; stick an NRF24 module and Teensy inside, some gimbals ...

It’s winter, and that means terrible weather and very few days where flying RC planes ... 3.5mm jack on the transmitter used for a ‘buddy box’, but [sjtrny] had an extra receiver sitting ...