Here is a great idea. AN auto-sprinkler for wandering dogs...but let's not limit ourselves here. This had potential for door-2-door sales people, Jehovah's Witnesses, and neighbors you don't like:
http://www.biconet.com/critter/sprinkler.html
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Another Cool Link if you like Crosswords (and aren't good at it):
http://www.ojohaven.com/fun/crossword.html