I have heard good things about the ones with the mobile pager systems that alert you when the alarm goes off. Im not too sure their specs, but they claim to have ranges of up to 1/2 a mile.

I was thinking about looking at one like this for myself. It would be nice to get a page, or a beep on my key chain signifying that my alarm is going off instead of going outside to find a rock through my windshield cause my alarm drove someone crazy. Plus I hear that some are fairly good systems regardless of the page feature.