[f5fstop]

That interface, as designed will not work on the Hummer H3; reason, the connector they show, is not used on the H3. In addition, they are turning the system on/off via the steering wheel switches which signal the BCM via the low-speed LAN circuit.
However, they might be able to make one for the H3. It is evident, by the connector they are using, they are somehow messing with the BCM signal via the low-speed LAN signal from the BCM to the NAV unit. So, since it appears the BCM is the controller of the functions, all they would have to do is figure out how to control the BCM signals to the H3 head unit.