In the last two days I've written a small program that allows you to utilize part of the built-in firmware update mechanism of the Motorola EZX phones. In fact, what it does is to download an arbitrary (max 1MB) piece of code from the PC to the phone via USB, and then execute that code on the phone.
On the one hand, this might look like a security hole (but well, nobody really cares about security on mobile phones anyway). On the other hand, this should definitely speed up kernel and driver development within the OpenEZX project, since it basically removes the need to flash the phone for testing of some new code.
Also, once a working driver for the TransFlash slot has been cooked up, it would actually be possible to usb-boot the phone into an OS that mounts its files from TransFlash. This doesn't touch a single bit of flash memory and is therefore ideal for development and probably even something similar to what 'live CD' distributions are to PC systems.