The adapting Verb shoes from VectraSense Technologies, an MIT spin-off company, have been in development for a while, but now they're finally ready to buy. They're not quite Marty's amazing Nike's from Back to the Future 2 but they are clever: the built-in twin air bladders are controlled by an on-board computer that detects what activities you're up to and adjusts the air pressure accordingly.
The idea behind the design is that the shoes are always comfortable, adapting dynamically. And if that's not 21st Century enough, then the shoes also have built-in wireless networking which can let you swap contact info with other Verb wearers nearby, and connect up to a PC so you can access the autocomfort settings. Activating the wireless mode is achieved by tipping your foot vertically and holding it for five seconds, so you shouldn't trip it off accidentally.