On Friday, October 26, 2012 6:39:14 PM UTC-4, Paul Remde wrote:

The bummer is that even though it is possible to connect a GPS up to the
Trig TT21 or TT22 an send ADS-B data out, the FAA says that is illegal.
They say you must use an approved GPS costing $3000+.

A quick list of the approved GPS position sensors and prices

Freeflight 1201 WAAS/GPS Sensor $2,919.00
Freeflight 1204 WAAS/GPS Sensor $6,889.00

Could not find prices for the NexNav sensors:
NexNav MINI WAAS/GPS Sensor
NexNav MAX WAAS/GPS Sensor

Is NexNav shipping these products?

Maybe the price will come down when more than one vendor is shipping approved products.