I have a Nikon d3200. It has got all the basic features a photographer probably needs.
Why I want to use a smartphone to control camera is because,
Sometimes its flexible.
An added swivel LCD screen.
To add HDR and auto bracketing in my camera's feature list.
May be more, which I haven't encounterd till now.
If I add a wireless module (my camera supports Nikon's wu-1a) in the camera, than is the following procedure possible,
1) From the camera,
+ Frame a picture on tripod
2) From wirelessly connected smartphone
+ Control exposure triangle + Select between single shot, HDR, Auto bracketing etc + Start capturing