WiMax is already available in a couple of cities in California and it won't be long before T-Mobile and Verizon roll it out elsewhere. Right now, with your iPhone or a Palm Centro, you can stream internet radio through the auxiliary input jack standard on most car radios for the last two years.
Ford's Sync option and a similar device Cadillac is making available allows you to in effect create your own WiFi space with a 10-20 ft radius around your car based on cell phone technology with a $30 per month subscription...we're only a couple of years away from this being widespread.