KeySweeper is a stealthy Arduino-based device, camouflaged as a functioning USB wall charger, that wirelessly and passively sniffs, decrypts, logs and reports back (over GSM) all keystrokes from any Microsoft wireless keyboards (using proprietary 2.4GHz RF) in the area.
Keystrokes are sent back to the KeySweeper operator over the Internet via an optional GSM chip, or can be stored on a flash chip and delivered wirelessly when a secondary KeySweeper device comes within wireless range of the target KeySweeper. A web based tool allows live keystroke monitoring.
By Samy.
(via)