BJ Fogg is doing interesting work on that mobile-persuasion subject at Stanford. I remember reading one of his papers that had a quite helpful evaluation of what kind of health regarded persuasion aspects are supported by mobile technology - as a simple example mobile tech having a disadvantage in starting a new behavior, but strong advantage of training an existing one over (ir)regular intervals. It is quite a fascinating subject ( http://www.mobilepersuasion.org/ ).