I've already got a disk lock but I suspect it can be broken into easily, it's mainly a visual deterrent to get them to move along the line of bikes at work and not go for mine, I don't always fit it either....
The type of alarms I have seen are cheep but i'm not keen on wiring it in to immobilise the bike, the sort I have seen fit under the seat and go off when the bike is moved, hopefully this will be enough for them to leg it. My garage is also away from the house so not much chance of me hearing anything else but a loud alarm.
