Coastaletech in an email indicated that it should work but isn't "officially" supported or documented. Since our Enclave probably won't arrive before Christmas I won't be one of the first to offer my experience on the installation and function. :
Technically, yes, I think it voids the warranty on any equipment altered or affected by aftermarket components. You'd have to read the fine print on the warranty to get the complete official policy. Unofficially, if it is plug and play then it is pretty easy to unplug and remove before a trip to the dealer. I'd feel unethical about doing that if, for instance, the sat nav started acting up, but if a button broke on the front of the nav unit that had nothing to do with the lockpick and everything to do with bad craftsmanship then I wouldn't have a problem with it.
Did a little more research on the warranty issue. Seems that the letter of the law, according to the Magnuson-Moss act of 1975, prohibits manufacturers of products from denying warranty claims if an aftermarket part was not the cause of failure of another part. i.e., they can't deny warranty work on your engine because you added aftermarket speakers to a vehicle.
In the case of electronics plugged into the Nav unit, you will be fighting an uphill battle if you ever have a problem specifically with the Nav unit. Burden of proof should be on GM, but the real world doesn't work that way and it would be left to you to prove that the aftermarket module could not have caused the problem.
I have been seriously considering it. However I do not want to mess with such a beautiful car yet especially since it involves removal of trim pieces. I think once CoastalTech states its fully supported and 6 months down the line I will splurge and get a combo of Ipod control and the Super LockPick.