A few weeks ago I bought the mini OnGuard lock (to use with my massive thick chain) and four OnGuard cable locks. For the most part, they seem effective, but unlocking them can be a pain. Often they stop the key from entering all the way and I have spent several minutes trying to insert the key fully in order for the release to activate.

Recently, I saw something about bike alarms (think it was on the net). Does anyone have info on these and whether they are a sound investment or not?