Data collection with Android via USB

What would be the best way to access the USB as a serial port on an Android device (HTC Magic)?

I am thinking about an OBD-II interface. Can I do this on a standard phone or more likely will I need a modified firmware?

Can data be transferred through USB cable?

With a USB cable, connect your phone to your computer. On your phone, tap the "Charging this device via USB" notification. Under "Use USB for," select File Transfer. A file transfer window will open on your computer.

According to this post, Matt Porter presented a review of Android at the Embedded Linux Conference Europe. I mention this mostly because of the example used to describe the current state of Android.

"Just one more practical example: You cannot even plug a USB drive to an android system, since /dev/sd* is not an expected device name in their hardcoded hotplug management.

Executive summary: Android is a screwed, hard-coded, non-portable abomination."

I'm sure someone's working on it, but I'm afraid for now you're out of luck unless you're willing to go low-level and edit the OS.