My garage is reasonably secluded - behind tall gates and at the end of the garden. This is good, because people passing don'y really know it's there, and I'm particularly careful to never open the up and over door and gates at the same time, so all anyone sees is the front which looks like a typical double garage.
That said, being tucked away is also good news for anyone trying to break in.
The steps I plan to take are:
Install a mulitpoint lock on the PA door (5 point lock)
Bars over the windows.
Blinds over the windows (as at night, when I'm in there, it's easy to see from other properties what I'm doing and what's inside.)
Night vision camera (more for my own peace of mind to be able to look in there remotely if we hear noises but can't arsed to go down and look.)
And then an alarm.
I'm happy to install it myself, but am not sure about how reliable wireless ones are. I think I'd want:
Door / window sensors
Window vibration sensors
I don't think motion sensors would be worth while, as there's only 2 doors and two windows, and if these are hooked up, motion detection inside would be pointless, right?
Oddly, no visible bell box on the outside, as I think this suggests there's something worth breaking in for - maybe with wireless this could be on the rear of the house instead.
A ludicrously loud siren INSIDE the garage with a strobe - making it an unpleasant place to be. We had this installed in a computer parts place I worked at, and when I was inside and it went of it was unbearable - to the point where you couldn't communicate or think straight, and were completely disoriented.
Some of them will ring you if they go off - again, useful for remote notification and then having a look through the camera.
It would also be useful for the alarm to disable the lighting circuit too, but I can probably manage this with a relay running off the bell box.