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Use Linux or Microsoft Windows, the open source sndpeek program,and a simple Perl script to read specific sequences of tonal events - literally whistling, humming, or singing at your computer -- and run commands based on those tones. Give your computer a short low whistle to check your e-mail or unlock your your screensaver with the opening bars of Beethoven's Fifth Symphony. Whistle while you work for higher efficiency.

O'Reilly Radar Release 2.0 'magic' link.

Coverage and comments from Lifehacker

Interesting implementation example at:

Demonstation video of raising and lowering windows on youtube

IBM developerWorks podcast with Scott Laningham.

Original link at IBM developerworks. Please use the cached copy if the link is dead.