So apparently Bluetooth in-car speakerphones have become totally awesome while I wasn't looking. There are a bunch that will read text messages to you while you drive and allow you to dictate text responses. Here's one:
http://www.motorola.com/Consumers/US...Roadster-US-EN
The problem is I can't find one with this text reading and dictating functionality that is compatible with the iPhone 4. Anybody know if such a beast exists?