The technology has been there for quite a few years - the big plank wing stuff already uses them - and they may be a wonderful idea but no matter how light.... weight ... emc ... c of g ... and the high the cost of certification may well be why they are not already in your favourite rotary craft.
Aside from that - would you be able to mount such a camera in a position that gives you a view of the bits that might hit the scenary without resorting to a 'fish-eye' lens that would badly distort your view?
Finally [from me anyway] - would the CAA allow you to land watching a monitor rather than out of the glazing .... ?