Some of the sites have videos.
I have one... I use it to keep the dogs from running up and down the fence barking at the neighbor's mutts. They learn really quick how far it will reach, though, so I have to move it around.
I also tried setting it close to the bird feeder to deter squirrels; it has to be really close so the birds are above it's field of vision, but it will definitely set a squirrel packing!
For a practical joke you can put one next to your driveway...
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Willie
She's a tired old barge but she's paid for!
http://s71.photobucket.com/alb...p;current=ef324993.pbw