This is the cheapest wireless link I could find... Problem is that it only works with 5 Volts (despite what the walkthrough says) and the receiver output is very weak. Took a while to get it working with the Prop, but here's how I got Prop-2-Prop wireless comms going:
Transmitter:
Note: I used pull-up to 5V and set mode bit 3 in "FullDuplexSerial".
Receiver: