Well, that took a while. AppleInsider is reporting that AT&T has now agreed to let SlingPlayer for iPhone [US$30, iTunes link] stream over the 3G network.
When the app was released last May, there was great moaning that the SlingPlayer Mobile app only worked on a Wi-Fi connection. That was in contrast to other versions of the Sling app running on other phones like the BlackBerry, Windows Mobile and some Palm devices -- all of which were allowed on the AT&T network.
AT&T now says they have worked with the Sling Media developers, and found ways to reduce the bandwidth footprint. Getting it all up and running will require a new version of the Sling App, which should appear shortly. The app will be a free upgrade for current owners. The posted version was released in August of last year.
A source at Sling Media told me this morning they were glad AT&T "finally saw the light." We'll keep you posted on developments, and we'll test the new app when it's online.