PumpTire, the bike tire that auto-inflates as you ride.
The PumpTire system is so simple it's pretty surprising something like this isn't the norm. It uses a valve along with a special inner tube, working in conjunction, to tell when your tires need a little more air let in and when they're full. That's really all it is — no embedded motor or anything fancy. And nothing that'll have you using your bike any differently.
Imagine taking your bicycle out of the garage and never having to fill up the tires or even check the pressure. Or imagine yourself being able to change your tire pressure on-the-fly with a simple adjustment from the handlebars.
More information, and support it on KickStarter.