Waterlogue is an inexpensive app for the creative types. $3.99 – cheap.
The app is available for PC’s and Macs, as well as iPhones and iPads. I use it on my Windows laptop when I want to develop digital artworks, or just feel like playing around.
For the student, it can help you learn how to translate scenes into watercolors. It will turn any photograph into a watercolor version. Of course it is no substitute for actually painting, but is a useful resource for getting ideas.