I had been searching for a traffic counter with a dedicated iPhone interface that I can access on the go for some time, and it turns out that good solutions aren't really that many. There's Mint, which you have to host yourself. There's the Analytics app for iPhone, which is a mobile interface for your Google Analytics account. I tested, I think, every single one of those apps, and Analytics is by far the best, but it comes with all the limitations of Google Analytics itself, most importantly the reporting lag.
Then there's Clicky, which is a hosted service that offers an iPhone-like mobile web interface (the screenshot above), real-time reporting, and detailed activity logs for each visitor. Clicky comes in a variety of plans that range from free to $20 a month. I've been a happy customer of their $10/month Pro plan for half a year now and am happy to recommend them.