This is a very interesting security apparatus. My friend has one of these at his house and he likes it quite a bit. This system is wireless and costs about 80.00.
You can add additional transmitters/sensors as you feel the need. So it is quite expandable. I think I have seen these at Radio Shack before. I tried my friends and anytime someone would go near his vehicle the system would alert him to what was going on. It seems to be a good way of letting you know if you have any unwelcome guests around your property.
The sensors are kept outside and are quite weatherproof from what I have seen. They seems to have quite the range. This unit has additional provisions to add sirens or flashing lights and external alarms should it suit you. I am thinking of getting one of these. I have an electronic security system at my house but it does not let you know whats going on with your outside yard or vehicles. (I did not rate the monitoring above as it is not hooked up to an independent security monitoring company.)
My next door neighbor recently had his vehicles busted into in the middle of the night. He sure could have used one of these. His truck alarm did go off but by the time he got out there they had already busted into his truck and wifes vehicle and made their escape.These days the more of these things you have the better off you and your family are.