This technology already exists and is used - my kid brother used to fly Sea Kings on search and rescue and anti-terrorism missions. When hovering with a sonar buoy dropped, they push a button and they hover at fixed height and position. Admittedly he did say it was utterly boring and he has since moved to Gazelles - apparently like going from driving a bus to a formula 1 race car.

Oh, and there are a couple of helicopters which will fly inverted. The most famous is the Lynx. The critical issue is that most choppers have blades which flex - they bend up when lift is applied. Normally this is fine, but when inverted this bend means the blades will chop off the tail! Barrel rolls are fine as the centripetal force means your feet always feel 'down' but you need rigid blades to do 'real' inverted flight. And it isn't recommended even in a Lynx, as this brings it very close to limits.