Smith & Wesson motion detector alarm - 80% off
That's some cheap way to feel more secure in your home. This unit can be secured to a wall near doors or windows (no drilling or wiring required), where you can activate it with a personal code. Any movement in the 20-foot by 90 degree area will cause the unit to emit an ear-piercing alarm, which will hopefully send the intruder running (or you scrambling to find the paper you wrote your code on). The unit uses 4 double-A batteries (not included), and comes with an AC power input (plug not included).