Just going of at a slight tangent, I watched one of those police programmes recently on the BBC, featuring in that episode the Humberside police. What struck me was the resources they were using to solve relatively minor crimes. The police helicopter spotted two youngsters break into a parked home delivery van and steal "a parcel" from the front seat.
They tracked the youngsters to a house on a rough housing estate, and eventually the ground-based police (in quantity) entered the house, recovered the parcel, it contained a pair of ladies boots. The thirteen or fourteen year- old was taken in, given a warning and sent home. As a policeman interviewed said, the lad will be out thieving tomorrow, and the next day, and implied that the police actions were somewhat futile.
I fully accept that the police should seek to stop or solve crime at any opportunity, but I wonder what the cost was of using the force helicopter to solve that particular crime?
Surely there has to be proportionality, and expensive assets such as air support used to solve the more dangerous incidents, like the high-speed car thefts, or other major incidents?
I guess this does not really help you with your "Skywatch" discussion, but on the subject of microlights wandering around in urban areas, earlier this year my wife and myself witnessed a quite frightening incident from our back garden where a microlight flew across the approach to a local military base that has intensive helio activity just as two helicopters were making an approach in formation, and both had to take serious evasive action to avoid a mid-air. This was just inside the edge of the circle on the charts denoting the area of intense activity, but if he was a local, he should have known about the low-level military traffic patterns in the area. The microlight appeared to "pop-up" from very low level right infront of the two military helios.
So, I'm not convinced about "amateurs" ( in the context of air-ground observation for crime) getting involved looking for problems on the ground. Leave it to the professionals, and concentrate on looking what is happening around you in your immediate airspace please!
EGCA