Well doing a little searching it looks like the Porsches have a CAN-BUS system....so you would need an interface to run it properly...doing a little more searching i find this:
http://ifar.ca/en/vehicles/porsche/cayenne/2008/

looks like you can interface an alarm with this unit and run the options you want...from reading on the boards it looks like most avoid doing these types of systems cause of headaches later :(

Thanks Wally. I have basically come to the same conclusion as many. Not worth the headaches.

Sam

i have read a few boards and it looks like there are a few that have done it....but they say it sets them back $2k for the whole setup with alarm!!! :eek:

It is possible. The Clifford alarms are manual transmission safe. There's a procedure that consists of pushing 1 button before you get out of the vehicle. Basically, you pull up to park, press/hold the foot brake, pull the e-brake, release foot brake, press button on remote, turn ignition off remove key and get out. The vehicle is still running. WHen you press the lock button all doors lock, alarm arms, and engine shuts off. When you return it will remote start. If the alarm is triggered or disarmed first, it will not remote start.