The UK is pushing forward with helo UAV's in preparation for the London Olympics...these platforms are unarmed surveillance only, as are most manned police platforms, (ie the platform itself is not armed)
UAVs have to have their own backups, and have to be proven to be safe enough for the intended work.
Depending on the platform, most have multiple redundant systems, and have coded procedures on disconnect...
I would trust most of these UAS platforms to put my children in the back, rather than most GA aircraft I see in the skies...