I’ve been playing with a slick App.net client called Rivr in beta for a while now and it has just been released on Apple’s App Store. The client is one of the coolest I’ve used on the iPhone and displays post data like images and locations in very cool ways.

Rivr developer Tony Million used a feature of App.net called annotations to implement all of the slick media behaviors in Rivr, and to prepare it for the future. Annotations are bits of metadata that are attached to each post. They can contain a variety of things that don’t add to the 256 character maximum of a post.

Twitter actually saw the power of these annotations and announced that it was going to bring them to its service, but never delivered. App.net added them just a few weeks ago, and they made Rivr possible.

image 4 520x923 Slick App.net client Rivr uses annotations to beautifully display images, locations and more  photo 121 520x923 Slick App.net client Rivr uses annotations to beautifully display images, locations and more

The app is a single-column browser with a stream of beautifully presented images and posts. Each bit of data that you attach, like a location, also gets its own formatting and presentation method. You can also post things like your mood, the music you’re listening to and your location from a sidebar that you access via the plus button or a leftward swipe.

image 5 520x923 Slick App.net client Rivr uses annotations to beautifully display images, locations and more  image2 520x923 Slick App.net client Rivr uses annotations to beautifully display images, locations and more

The image posting is well done, with a built-in set of Instagram-like filters that you can apply before you post your image. I do wish that the filters were more photographically sound, though. Most of them are either so subtle that you can’t even tell the image has been changed, or way over the top. Hopefully these get tweaked down the road.

Oh and then there’s this slick pull to refresh implementation:

Rivr Slick App.net client Rivr uses annotations to beautifully display images, locations and more

The annotations are what gives Rivr its juice, but they also allow the app to keep the data it uses around for future changes and features. Much of the data that the annotations record is behind the scenes, and will allow for analysis of the data. Every photo uploaded is an annotation, as is every filter that is used and there’s a version of the photo preserved in the data of each post as well.

“The idea,” says Million, “is we’ll be able to produce stats on the most & least used filters, some other things that will be coming online in future versions, every location checkin has a foursquare venue embedded in it, so we’ll be able to do stuff with that too.”

A swipe to the right brings up a browser menu that lets you jump to your various sections of App.net and all of the animations and navigation is smooth. There’s not a whole lot left wanting in this first official release.

The app is free on the App Store now, so I’d suggest you check it out if you’re an App.net user.

Rivr for App.net