what you gotta decide is this, would you want a motion detector, get woken up by 2 or 3 morons that want and are going to nick your gear or sleep through it? if you want to be woken come out and have a go and probably get a damn good kicking then get a motion detector, if you would rather wake up find your stuff gone and be safe to go home to your wife and kids then dont get one.
i am the type that if i wake there is no way on this earth some piece of scum is gonna take my gear without a fight and for that reason if it ever happens i hope i am asleep, my gear is insured and if i have to i can live without it. my wife, kids and grandkids however will struggle if i am laid up in hospital out of work, OR DEAD.
have heard that it is gangs of gypsies touring from area to area, a couple doing the stealing and a couple watching out