A new study predicts lots of Wi-Fi in cars in the near future: In 2008, according to research from ABI, 25 million cars will have Bluetooth or 802.11 gear. There's been a big push to get Bluetooth in cars, but that will support limited applications. Apparently, car manufacturers are looking at what type of technology will enable wider area and higher bandwidth applications. Wi-Fi seems an obvious choice.
I was at a conference recently where someone envisioned a Wi-Fi-enabled car pulling into a gas station on a road trip and downloading music from the gas station. Then when the person gets home and pulls in the garage, their home Wi-Fi network downloads the new music from the car to the user's home music collection. That would be cool.