There are a number of Remote Starts that will work with your car, the only problems will be finding a Reputable Installer / Shop that knows your vehicle. While it is somewhat a typical installation, your vehicle has a Transponder & you will probably have to use a Universal Transponder Box (lose a key), inwhich one of your Ignition Keys is put inside a small box & hidden under the dash with the Remote Start.I like the OMEGA or MICRO ALARM products myself. They have proven to be the most reliable for me.
If you need a wiring chart, let me know & I can post it
Audi Dealer would be my last resort....sorry........unless the Dealer has a Audi Parts Remote Start & they have installed before.To many times have dealers called, because their Technician wasn't able to fully understand the install procedures & instructions. (not specifically Audi)
As far as Warranty, I would want to call Audi Service ( not the Dealer) to verify, but I have not heard of Warranty problems, unless there was a blatant mess up in the installation
I usually compare 2 charts:This is what I have: