This question has appeared recently atr the realms of the CAA.
Basically, Skywatch is an initiative to get aircraft owners to be willing to help out in such situations as missing persons.
A good friend of mine recently became on of the first helo supporters with his bell 47.
The CAA were not very happy and did deem it commercial work. But they have agreed to turn a blind eye so to speak as it is for a good cause.
The police/authority don't commandere (sp?) they just ask 'if you are flying in THIS area will you keep an eye out for.... (pretty please).
But, as a very soon to be commercial helo pilot, i wander, is it taking potential work away from the likes of myself who could (with an AOC) charter a helo to the authorities and then start to recooperate my expenses so far?)