I heard about this app the other day, and had to check it out.
Bikesavr is designed to help those of us who use roof-mounted bike racks to remember that our bikes are on top before we pull into the garage, and damage our bicycles - something which has happened to me (well, my wife) before.
How it works, is the app sets up a GPS perimeter around your your destination - which you can either select by using your current location, or by entering an address manually. When your phone crosses this line, an alert sounds to remind you that your prized posession up above you.
Set up is simple, you need to make sure that your notifications are properly set. Also, make sure that the sound is turned up on your device.
After you enter the destination address, you push the "save my bike" button. You can create a list of commonly visited locations, and select from them. There also is a list of several alert sounds you can choose from.
Once it is active, it will run quietly in the background. The geolocation technology will check your location occasionaly to conserve your battery life. As you get closer to your target location, this frequency will increase.
I tried it out on my commute home. I don't know the exact distance that the GPS "fence" is from your set location, but it seems that it is about 0.2 mile or so - plenty of time to remember that your bike is up top, but not so far out that you could become distracted and forget.
My only complaint is that the alerts aren't annoying enough. I initally had it set on "siren" and when it went off, I was looking around for the police car.
The app is $0.99 from the iTunes app store, a bargain for helping to protect what for most of us is a very expensive investment. It won't replace my current method of hiding my garage door opener in the glove box, but used in conjunction with that method, it should prevent me from future mishaps.