Road Angel Connected no question (imo) the best thing out there.
not cheap but depends how much you value your license and I don't mean for getting away with raking it about all over the place I mean doing 34 in a 30 and getting points and a fine
It's around £399 and £4.99 a month
Updates every 2 minutes via a built in sim card (orange network)
The only unit (that I know of) that has 'live' camera warnings - it works by users adding live vans as they pass them and I believe that road angel group add them as they are released on police websites too?
I was near Warwick earier this year doing about 75 on the dual carriageway and the 'live' warning went off - about 10 seconds later I saw the mobile camera van up on the bridge.
Priceless for me!!
I had a snooper back in the day then moved to Road Angel a fair number of years ago - although I never really liked how they looked the database is well known to be among the best. The latest one can't be touched with the unique 'live' feature.