I would like to use Android phones as a way to do some processing and visualization of a sensor that would be attached to the USB port on the phone. The sensor would plug in
This guy has modded his Nexus One to work as a USB host and has done several cool things.
He uses a USB keyboard and runs a movie from his USB stick. Then he runs a webcam through the phone and displays it on the computer and even runs an entire desktop-based Linux distro from his phone onto his computer monitor.
Pretty amazing stuff.
http://sven.killig.de/android/N1/2.2/usb_host/