Sonar Based Power Management For Your Laptop Display.
A research group at Northwestern University and University of Michigan has released open-source display power-management software that uses a new user presence detection technique. The goal is to shut off the display immediately when the user leaves the computer rather than using slow and error-prone mouse/keyboard activity timeouts. Surprisingly, the mic and speakers of many laptop computers are sensitive to ultrasonic frequencies. Those frequencies can be used to silently probe the laptop's physical environment. This software is based on research published at the UbiComp2009 conference. A Windows binary and source code for Windows and Linux are available for download.
Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace. -- James Madison
The Constitution shall never be construed to authorize Congress to prevent the people of the United States, who are peaceable citizens, from keeping their own arms. -- Samuel Adams, Debates and Proceedings in the Convention of the Commonwealth of Massachusetts, 86-87 (Pearce and Hale, eds., Boston, 1850)