If there is one key feature that has been missing from the iPhone since the beginning, it is the ability to use the iPhone as a tethered modem to surf the Internet. Well, during the Q&A session at the Apple event on Wednesday, SVP of iPhone software Scott Forstall, hinted at the presence of this feature in OS 3.0, but sated that it would rely on the commercial and technical support of individual cellphone carriers.

     On Wednesday, a few hours after the event, the beta of the 3.0 SDK was seeded to the developers. One developer in particular who got to work on the new OS straight away was Steve Troughton, an iPhone developer in Ireland. He was busy tinkering with the carrier settings files, trying to overwrite the default settings for his local carrier, O2, when he successfully, albeit unintentionally activated data tethering on his iPhone.

     Now while the feature is obviously still very beta, he was able to connect to his Mac via USB, and indeed got 3G access to the Internet, just as though it was a normal network adaptor. As you can see from the images above, the feature is exposed as a simple “slide to activate” screen, complete with instructions on how to connect via not only USB, but via Bluetooth as well, but it has not yet been tested over Bluetooth. The second image also shows that when connected, a blue status bar appears at the top of the screen, much like when you are on a call and deviate away from the call screen, and reads “Internet Tethering” to alert the user to the fact that they are still connected.

     It is not clear as yet which carriers, if any, allow tethering at the moment. Some already offer data tethering plans for other handsets, so it wouldn’t be a stretch to imagine that they could easily implement the plans for the iPhone in the future.