Ok, well here's a response that goes the geek road. You could always build this system yourself.I'm strictly a DIY type of guy...
For my senior design project for my Bachelor's Degree I built an ad-hoc wireless sensor grid. I tied an infrared trip sensor ($14), a motorola 6812HC microcontroller ($50) and a transceiver (free) to make a small wireless sensor unit.
I set up 4 of these units on a floor of a building (IE windows and doorways) and had one unit connected to the serial port of a computer to be the base station. I wrote some basic networking protocols such that when one of the sensors on a unit went off, the others would relay the data until it reached the unit connected to the computer. At that point I could make the computer do almost anything from setting off a sound, post it on the internet or broadcast back to the network with an alarm (IE turn on the lights).
One of the uses I cited for this project was home security. You could set up dozens of these in a 100 yard radius. As long as there is a path along the network such that a signal can hop all the way to the base station you can monitor a multi-level office building. The difference between this and current home security systems is that you have the freedom to configure it to more situations. You can place the units wherever you wanted, you can replace the infrared trip sensor with longer/shorter ranges, a laser sensor (IE monitor a door from far away), a microphone to detect noise, a pressure switch for windows/doors or even a combination of sensors. I made it such that each unit can take on a 9 V source from a wall jack or a battery so that you can have permanent units inside the house connected to a wall jack, but also have ones outside as well.
I still have my prototypes from this project, so if you ever wanted to build this yourself I can certainly help direct you. From my research 2-3 years ago I couldn't find any commercial product like it. Most are set it and leave it type of systems that are very rigid in terms of configuration.