Twitter's Jason Costa announced "Following last week’s wider release of photos to Twitter.com users we’re ready to share our media upload API which will allow developers to conveniently attach an image to a Tweet" .
He added "We’ll soon incorporate this service into Twitter mobile clients as well" .
Besides the obligatory technical details there are few interesting things in the blog post announcement. For one Twitter is moving rather fast to make the API available to all developers.
At this point third party clients as well as other apps can allow users to upload photos directly to the site like Twitter.com currently does.Note that Twitter's own apps don't have the functionality yet so third-party clients could incorporate the feature faster than the official apps.
That said Twitter must be well under way in adding the feature to its own apps and while it has not provided a time frame support should be coming in the next month or so.
Another subtle change is that the photo uploads via the API use the uploads.twitter.com URL rather than the common api.twitter.com. This Twitter says will ensure higher availability for the service always a plus.
What's more Twitter seems to have designed the API to be media-agnostic i.e. be able to upload more than just photos. Twitter hasn't said anything about this type of functionality but it's probably thinking about it and most likely wanted to make it easier to incorporate things like video in the future if it decides it wants to.