Snoopers are nice and compact, but they suffer from false alarms, as all makes do. You learn to ignore the false alarms, though. I find the Snooper to be a little loud on the quietest setting - it would be better if it used ramped volume. Still, it's saved me a few times :P - worth the £170 from www.letsbuyit.com. I usually hardwire the unit to, say, the overhead light and put the unit at the top of the windscreen. Less obvious there.
By the way, aren't the blue cameras on A and B roads traffic sensors for TrafficMaster? They measure traffic flow, not speed.