Okay, your GPS outputs its data into a device that is hooked up to a transmitter that transmits your callsign and GPS location at (say) 2 minute intervals using standard AX25 packet protocol. Receivers in other planes pickup the transmission and a device decodes the packet of data and displays on a map (on an ipad or similar device) the location of that particular plane. The idea is not original, us Ham radio operators have used packet position reporting for yonks. So, all you modern electronics wizards that are into FPGAs and stuff, stop interfering with the girls, put down your drinks and start working on it. I'll keep the coffee coming and provide the pizza. If the display software was designed well, it could be used like TCAS and warn the pilot of possible conflict, although I haven't included altitude in my idea (starts to get expensive).