There are some guides out there on how to write your own plugins for iSync, but most of them haven't been updated for the changes that 10.4.7 made to the plugin structure.

Also most 3rd party software doesn't seem to support that phone yet, so I think you're out of luck at the moment as far as syncing software goes.

But here's another idea:

Click on the bluetooth icon and select 'browse device'. Then select your phone in the selection dialogue box (bluetooth must be on and the devices should be paired). YOu might be able to navigate through the folder structure on the phone to the address book storage folder.

Then you'd just have to dump all of your vcards into that folder.