I now know of three mobile Steem apps.
By Matthew Brady, Public Domain
@steemapp's Steemy is written in native Swift for iOS and Java for Android. @str11ngfello is doing the iOS version. @cyonic is working on Android. They plan to open source the crypto, but not the rest of the app. They tagged their single article so far with #steemy. They've promised a public beta soon. This is the most featurefully promised of the three.
@riensen's Steem app is iOS only. Looks nice. Open source (github.com/riensen/steem-app). Riensen has been helping me to get it to build on my Mac. They say they have a public beta, but my email asking for it went unanswered. No news since the announcement almost three weeks ago. And no GitHub commits.
@good-karma's eSteem app is written in JavaScript and HTML, using the Ionic framework. This makes it portable to both iOS and Android. It is also open source (github.com/feruzm/esteem). His frequent posts about it are tagged as #steemmobile. GitHub commits are also frequent. It is already available on the Android Market, and they're waiting for Apple to approve it for the App Store. I've gotten it to work in the iOS simulator on my Mac, and in my browser, using the Ionic web server. But they've added a lot since then, so I won't comment yet.