UAV hover with centimeter level precision is trivial and a regular feature of high end UAVs. Recently I was writing some UAS requirements and one can now purchase, off the shelf, mm level survey accuracy, no fuss, no muss.
Similarly, long duration tethered UAV systems are available off the shelf, all pre-engineered, from a multitude of sources. Simple Google "tethered drone".
It's not too long from now when public safety services will have a fleet of UAV trucks with both tethered and un-tethered UAVs for deployment to both emergent situations and scheduled events.
Already seeing UAV power line inspection in my local area.