No mention of an official app, there's only the responsive style which I believe is having an overhaul for the next major version (2.0).
There is one already released in the addon market courtesy of @vbresults and @Slavik is currently nearing final stages of a mobile application also. I'm not aware of any others but think there was a third developer testing the waters to see if there's a market for one.
I'm using the one by @vbresults and it works great. Push notifications are nice. The one from @Slavik is going to be a full app as opposed to a wrapper but the wrapper method works great if your style looks good in a responsive size.
The one by the other developer that @James mentioned is only for Android and all it does is show new posts. No full browsing experience or push notifications.