Apple doesn't offically support the V800 phone yet, but a slightly modified iSync works fine. Essentially you need to alter the iSync binaries to treat the phone like it would the already-supported K700. After working out how to do this, I wrote a script that'll do the modifications. To make the changes, download the script to your Desktop then run it by typing the following into Terminal.app
$ cd ~/Desktop
$ sudo sh change.sh
It will ask for your normal login password. After you reload iSync, you should now be able to add the V800 via the Devices -> Add Device menu.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20041118143359172