That's totally a big area, yes. And if it's what excites Chris, then he should totally go for it. But it isn't my first recommendation, because most mobile apps are written in Objective C or Java, while Chris has learned Python. There's a fairly large amount of new stuff that one has to learn to transition from Python to a statically typed language, so it's not the most efficient path to a working app.
(It doesn't feel that different if you have been programming for a while, especially if you learned a statically-typed language first, but you've probably forgotten about having to learn about covariance/contravariance/invariance, or about memory allocation, or about type-casting).
After short googling, perhaps this could be interesting: http://kivy.org/ An open-source Python library for making programs that run also on Android and iOS.
Lots of people (particularly people associated with LessWrong) are telling me I should become a computer programmer; in response I've taught myself a little Python using this site, written a couple Python scripts on my own, and just now sent in an application to App Academy. But if I don't end up going to App Academy, what's the best way to develop some actually marketable programming skills? I've heard people recommending getting involved in open source projects on Git Hub, but when I looked at Git Hub I found it overwhelming, with no idea of how to find a suitable project to work on. Advice?