The way the device works is fairly simple: most keyless entry systems (think the Audi key fob above and your garage door opener) use something called a rolling code. Every time you press the button to unlock the door, you're sending out a code which changes each time for security purposes. The only problem is once you use a code once, it works forever.
The RollJam, when placed in the vicinity of an intended target, blocks the wireless signal and records it for later use. Once retrieved, you essentially have free reign over the previously locked device.