I've been happy with this product so far (see link below)though I've had it less than a month. I figure it's all the alarm I'd ever need (it will serve as a visual deterrent and probably scare off curious kids and what not) since if someone really wanted my bike they'd just pick it up and put it in the back of a p/u and be off with it, alarm or no alarm. It also serves as a reminder that the disc lock is engaged so I don't have to mess with stickers, bungees, or other types of "reminder" devices.
http://www.xenasecurityusa.com/home/current/lock/
