could anybody tell me if these alarms are good my Scooby gete vandalised by my girlfriends ex will welcome advice

I'm not sure what a microwave alarm is. But if your gf's ex is vandalising your scooby, surely contacting the feds would be a better idea?

Microwave is basically a bubble you control the size of and is not affected by air currents etc. It needs a body of water to set it off (a person). 

 

I like em because you don't have to have those ugly ultrasonic sensors, you can hide the microwave module away in the roof lining or under a carpet.

 

I guess you are talking about proximity sensors if you are talking about vandalism. When I was in the trade we did quite a lot of those with the Clifford systems and they worked flawlessly. It is all in the fitting and setup.

Buy a big dog