I read last year the (Texas?) police had some similar devices in there possession. The ones the article talked about listened to lock frequencies and could then work out the unlock frequency from it. So the criminals would scan car parks waiting for people to lock cars that where brought in, wait for the person to leave, then approach the car and unlock it with the captured frequency.

I have no idea if thats what all these devices are, or how legit the article was, but seems legit to me.