Elistair, a French company, is offering smart tethering ground stations for small UAVs. These tethering
stations guarantee a limited height in which to ascend to, as well as unlimited power and a secure video down-link which is transmitted physically over a lightweight umbilical wire, eliminating the need for swapping batteries. This allows for the deployment of drones for events lasting several hours or even days with no gap in coverage due to battery replacement.
With continual flying possible, drones can be launched at festivals, sporting events, or anywhere large groups of people gather to enhance security. Tethered drones can also be launched in disaster areas to bring cellular or internet access to those affected areas. They can monitor traffic, or provide an eye in the sky for large construction projects where a fixed aerial viewpoint would be beneficial.
Elistair currently offers two models, each of which allow heights of 160 feet and 330 feet respectively, and provides customization as well. Both tethering stations support the DJI S900 and S1000, as well as the Yuneec H920, and several other professional level drones as well.
Check out Elistair's website for more information