Doesnt help that they are either lying or misinformed about how the Sentry Key system works. The below description describes how to bypass the Ford PATS system, and the GM is even easier, but the Sentry key is not quite the same. I'll be bolding the appropriate section.
3. GM's PASSlock II, FORD's SecuriLock, CHRYSLER’s SentryKey, and TOYOTA's Engine Immobilizer - These factory-installed antitheft systems consist of a miniature transponder imbedded in the ignition key head itself, which allows the vehicle's computer to identify the "real ignition key" and thereby enable the vehicle to start. Recently, a national automotive magazine published information on how to bypass these systems. All a thief has to do is cut the black wire in the three-wire ribbon cable located under the dash and measure the resistance between the black wire and the yellow starter wire with a volt meter. They then touch the two wires with the matching resistor and the vehicle will start. This sounds complicated, but only takes about 20 seconds to defeat. Also, there is a company that manufactures a product called the "No Key Required Bypass Kit", which bypasses the transponder key system in any vehicle made. A salesman might tell you that because of these factory-installed systems, you do not need any extra security for your vehicle, but this is NOT TRUE! Many vehicles equipped with these systems have been stolen.
Okay, here we go. The method descibed is ONLY for bypassing the PATS system, which does do a full algorithmic check of the TI RFID chip, which both the DCX and FOrd systems use. But then cripples it by only sending the "start enable" signal through the use of a resistance signal, as noted.
The GM PASSLOCK system is weaker, since as they DONT say above, it has no RFID component at all, only a simple resistor, of which there are only 9 possible resistances.
Now, the Sentry key, while being similar to the PATS, takes it to a whole other level. Not only does the Sentry module itself do the algorithmic tests, it sends the raw data the the vehicle enigine computer, which has to do the same algorithms, reach the same answers, and send those answers (not just a simple signal, but coded messages across the data bus) back to the Sentry module, which then compares the answers.
If they dont match, the vehicle stops after 3.5 seconds.
Lastly, those remote start modules must be programmed in, just like a key, which requires either both original keys, or the a special #K too, AND the vehicles PIN, which can nly be gotten from DCX by a dealer, and DCX logs who requests those PINS.
So, in the end, this ting is a waste of time for a Sentry key equipped car. To my knowledge, and I've spent three years looking, there has not been ONE verified instance of a Sentry key equipped car being hotwired.
And of course, this is where someone brings up the University of Texas Team that did crack an RFID system. With 5-6 undergrads, a whole lot of reverse engineering, a lot of spare keys, 12 inch access to a valid key, and a lot of computers in the back seat.