Steam iOS app to version 1.3, adding offline chat, push notifications and an overhauled friends list interface. On top of that, invites have now been moved to a separate section of the app and you can more easily tell if your online friends are on the mobile app or using Big Picture mode.
There's no indication whether these features will make their way into the Android app, which is currently at version 1.0.3. We've followed up with Valve and will update this post if we hear back.
The Steam mobile app launched early last year as a free download on Android and iOS. You can use the app to talk to your Steam friends, browse the Steam store and peruse community groups.