It can be used widely as it's also varying by size and camera properties, as you might now. There are several examples from law enforcement used by Police or Humanitarian response (see attached link). There are plenty of examples from agriculture, mining, environmental protection monitoring or even in tourism, sports events or marketing applications. You also need to be aware about the legislation where you aimed to fly your UAVs.
I will be using DEMs generated by UAV photogrammetry (Structure from motion and Multi-view Stereo) which capture a coastal dune field in many different seasons of the year. Thus, UAV here is applied to coastal geomorphology and management, and GIS and remote sensing techniques are in place.
Coupling sand drift rates and volumetric changes to climatic variations will be the next step. Dune crest automatic extraction is quite challenging given the detail that such datasets provide (0,1m raster resolution), but, I am very enthusiastic about UAV in coastal application but you know what?
As soon as I finish this project I want to try Kite Aerial Photogrammetry, given that kites over beaches are far less regulamentated, far more efficient in high wind conditions (carrying more payload and sensors at a time) and inexpensive.
At the moment we are using UAV to document and verify andean condor nest sites in the Ecuadorian Andes. Have used them in the past for mapping and monitoring protected areas.
I use a multi rotor. Condors get a bit nervous, sometimes they fly off. We do our best not to disturb them when nesting and never follow them if they decide to leave.