Hidden Dog Door

This idea is targeted at annoying soliciters and bible-bouncers who like to ignore the "Beware of Dog" sign on your door, thinking they can just put their foot in front of the dog door to keep the dog in, leaving them free to knock at will.

Basically, it's a tunnel from the house to a hidden doghouse at the edge of the lawn, obscured by bushes or some other camoflage so nobody can suspect a dog is there. Simpy post a sign on your door warning that a dog will attack if you knock, and train your dog to attack if someone knocks (tell anybody who you want to come in to use the hidden doorbell). They'll never see 'im coming, because the dog will come out behind them.

The dog would (preferrably) be trained not to kill, just to rough 'em up a bit then let them go, so the newly-educated soliciter can warn his colleagues to heed the signs.