Ron Mowery posted a few weeks back on the grumman gang about a kit you could by and get ADSB up and running on a ForeFlight iPad for under 100 dollars. From Amazon:

Follow the instructions on the EAA site:

Took me about 25 minutes to do everything. I had to hack the Pi Filler code since the machine I run on is high security, but that was all it took. Plugged it all up, power on, viola, have a wireless station for the iPad to talk to.

Cheers

Roscoe

Here is a picture of the major components of the system. The Pi and power supply, the network wireless USB card, Vilrus R820T2 & DVB-T NESDR Mini 2 with antenna. Not shown – remote control.