It'd be nice, but it's sadly not possible at the moment. If I were to develop it, then that'd mean less time for me to do other things (such as a paying job!). Someone else could develop it, but making an app for the website is a very tall task. YWS has many of the same features as a site like Facebook; it'd take many, many hours to do. Then there's the necessary support and everything for it.
However, what I've been thinking is not an app to supplement the website but rather to complement it. For example, a story theme generator app, or a name generator app. Just really, really simple stuff. Creating an app that's just an RSS feed is also pretty simple. But, quite a ways off if it does happen.
