I haven't used that type of disconnect before, but it looks pretty trick!
However, here's what I've found when it comes to thieves: if the car doesn't start right away, they immediately go looking for the disconnect and your car is history. To combat that, I've used kill switch type setups with some built-in electronics that allow the car to start and run for about 6 or 8 seconds. Then the car dies, and unless the switch is thrown back and a reset button is pressed, the car will absolutely not start. This can be independent of any alarm system and costs less than $20 (only I forget where I purchased them).
I've confused the hell out of two different thieves who tried stealing my rides. I had a little repair work to do to the ignition, but I still had my cars!
Just my .02