For the course “Wireless and mobile network architectures” at KTH we had to come up with a paper. And as I was into NFC anyway I did something very related to that. A NFC Payment solution for hotspots. The idea is that you can use your mobile phone and its contract to pay conveniently for a hotspot. While this may not sound totally exciting it was a nice project with a working implementation. You can read the report or the slides.