Just placed the Crime Guard solution....
...on my web site. Really not too mystical, and no interference problems after 2 years on my 560SEL, though I have yet to get the 560SEL alarm to stop engaging if I program the 'lock doors on start' feature. I'll crack that one day when I stop fixing leaks on the 300SD.
The Crime Guard solution is ~$100 - buy your own relays and follow my wiring - there are a few reports of the Crutchfield relay holder (DSL-V) being wrongly wired. I know as I was one of their victims on my first install.
This is a 'high-end' solution in that there is a huge amount of programmability available - you can do it for less (e.g. JH Whitney's Valiant) if all you need is remote locking.
This system can flash light, blow horns, illuminate interior lights, lock on start, provide a panic alarm and starter disable. Heck, you could probably have fun with it on a date, too.
It uses rolling code technology to minimize risk from bad guys cracking the code.
Go to Cars - Technical - Chassis.