I have an older 2 way FM Compustar alarm/starter and am very pleased with it.
Take a look at biju's new 9000 model - it ROCKS!

Keep in mind that in order for you to alarm your rear door you'll need a pin switch. Since the rear door can only be opened by a key (unless you know were to reach if the spare tire cover is off..). It's a bit of a learning curve to remember to disarm the alarm before you open it with a key - unless you have a popper that's got some disarm logic in the alarm system... That's a future mod in the works for me...

With a good alarm system you can build on it with extras like glass break, motion sensor, auto arm logic... I'd also suggest a back up siren if the power is cut, and maybe a nice loud piezo siren in your dash to make it uncomfortable to be inside the car.

If cash is not too much of an issue - biju's working on a nice system with all the bells and whistles. Watch and learn, I will be.