Hey, you know that phone charger your girlfriend left in the outlet after she went to work? Do you know what it's actually doing? Could it be recording your computer?

This is the idea behind a recent hack by Samy Kamkar (maker of the Samy Worm and computer-hacking necklace). Kamkar figured out how to convert a small wireless charger into a spying device that will track a wireless keyboard's keystrokes.

Keystroke recorders are old-school tech that spies and agents used for years. However, most often require direct physical attachment to the computer in order to work. Kamkar's invention would allow for people to track this data without having to touch the computer. Not only can the device collect strokes in general, but if it detects certain strokes, it will grab a select portion of the text and SMS it directly to your number.

It stores the strokes internally. It also quickly charges. If for some reason someone unplugs the device, the charger will look like it powered down, but will continue recording the strokes until the battery runs out (Kamkar does not note how long the battery should last).

If someone wishes to build this device, Kamkar offers instructions.

The device will cost anywhere between $10 and $80 to construct depending on what features and parts you have to buy. The catch to this surveillance gadget is that it will only work on select devices; specifically Microsoft wireless keyboards from 2011 (though Kamkar himself noted that many of the older models are still being made).

While this surveillance gadget will certainly give you a reason to wonder whether that leftover USB charger is secretly tracking you, the odds are highly unlikely. However, this may give you some ideas next time you need to commit corporate espionage or something.