The idea is to see the process of it being drawn, for example as a changing background on your phone. Something you can do at the spur of the moment, like as you walk past the scene you'd enjoy seeing sketched, when you have your phone around, but not photoshop. Plus, does photoshop give you a live video experience how every line is individually drawn?
By the way, I had not heard of a sketch booth before and had to google for them. Thanks for pointing it out! My app basically aims at being your portable sketch booth with the added boon that it lets you watch the sketch being created.