I have been a bit behind the ball here. At least twice in the last month I have blogged about mobile search, but neither time did I mention the iphone tracking now available in Google Analytics – purely because I hadn’t noticed it had gone up.
So, now you can track users who viewed your site from the iPhone, simply by using this new advanced segment.
While this doesn’t track all mobile users, you can still try and use screen resolution stats to try and figure that out (listed under the visits stats).
(I don’t have any particularly mobile-oriented sites at the moment, this is the best screen shot I can do sorry).