I too have the A470 and attempted to use udumper, the camera seems to completely ignore the diskboot.bin file...
I figured it was worth checking to see if diskboot.bin was loaded at all, so tried a few others (camera worked as normal) and then tried a corrupt one - the camera wouldn't even turn on then. So I believe it's definitely loading the diskboot.bin files and the blinker method is needed?
Im going to dive into all this properly tomorrow, get a dev env set up and try to figure out LED addresses etc...any help is welcome =]
EDIT: I just read the thread above about the SD1100IS/IXUS80IS, chr's encoded blinker program gets my A470's LCD blinking =]