Amazon.com

Sometimes you just forget to close the garage door. But if "sometimes" is closer to "usually" for you, you may run the risk of having your garage emptied out by opportunistic passers-by, and you will certainly pay more to heat your house. Chamberlain's Clicker Garage Door Monitor helps you minimize the likelihood that you'll leave the biggest door in your house open. The device mounts easily without tools to your garage door via a Velcro strip; if your door is open, the sensor sends a signal to the monitor, causing a red light to flash. The monitor may be plugged in anywhere in your house where you're likely to notice the flashing light. Depending on your garage-door habits, this device could help prevent theft and lower your heating bills. Includes lithium battery.--Josh Dettweiler

What's in the Box
Sensor, receiver, AC adapter, double-sided Velcro fastening strip, lithium battery

From the Manufacturer

Did you close the garage door after you put the mower away? Go check now... You back? All good? Phew! But for next time, save yourself an unnecessary trip out to the alley with Chamberlain's garage door monitor. The garage door is big, and tough to forget to close. But, when you do, it's very likely that all those valuable tools, bikes, skis, and whatever else you keep in there won't be there by the time you realize what you've done. Chamberlain's garage door monitor lets you know if the garage door is opened or closed without the trip out to the alley in the middle of the night. The system installs easily with no tools. Just set up the sensor on the door, and set up the monitor in any room in the house. A flashing red light on the monitor means the door is open.