I'm fascinated with the idea of making a web application that functions as a mobile app as well. In practice I hear this doesn't work out particularly well, but, oh well, because you can get at two birds with one stone if you do it right, I think.
Recently, on the brink of my .NET skill, I was hoping to start work a mobile app for a company downtown in my hometown for a prospective physical therapy application. The plans for an app fell through and we sorted out other technical priorities to focus on.
Native mobile programming is non-trivial but Xamarin makes it easier. Hybridization and homogenization of an application is conceptually interesting to me - maybe someday soon I will have a reason again to try to pursue mobile.