Usually, alarms are meant to let you know when people are trying to get into your abode--unless you have kids. In the latter case, we need all the help we can get to track their whereabouts, especially if they have a penchant for bolting out the door and into the street.
The "RNID Contact Mat" is designed to provide just that. When the sensor-equipped doormat detects the pitter-patter of little feet, it fires off a wireless signal to a pager or a mobile receiver letting your know that the perimeter has been breached, not unlike those "Invisible Fences" used to track pets.
As Tech Digest notes, it can be used for adults as well, keeping housebound patients in and intruders out. Or you can just remember to lock the door.