Augmented reality applications to this point could be best categorized as tantalizing to the mind, but otherwise pointless. Thankfully, it seems as if that's no longer the case. AcrossAir, a nascent app builder for the iPhone, has conjured up a slickly executed digital guidance application that augments video with real-time distance and directions to the nearest subway station. With the iPhone 3GS pimping an improved camera, inbuilt compass and GPS, we had a hunch that it wouldn't be long before someone slammed them all together and gave commuters and tourists alike a reason to smile. Presently only capable of serving up directions in London, this app should find plenty of user interest that will hopefully drive its development for other metropolises around the world. Click through to check it out for yourself, and expect to see it ready for download as soon as someone (or something) at Cupertino decides to start approving live video programs. Any day now, Apple...

[Via Tokyo-Genki]