Anybody have one of those Magnetic Sensor Alarms for their garage?

Which is a good one? I was looking at this one, ( http://www.shopwiki.com/detail/q=Door+Alarm+with+Keypad/d=Door+Alarm+with+Keypad/jumpToFirst=t/ ) what do you guys think. I would need something that has a delay of at least 20 seconds and have some sorta keypad to disable it since im sharing the garage with some buddies?