To do this you will need to be handy with a text editor; I used vi because you need to tinker with files owned by root.
First off, backup the old data! (always a good idea)
% cd /System/Library/SyncServices/SymbianConduit.bundle/Contents/
% tar -cf ~/isync-backup.tar Resources
Now you need to edit some of the files in the Resources directory
% cd Recources
Make an icon for the phone.. I just copied one of the others:
% sudo cp N-Gage.tiff 6600.tiff
Next edit this file: SupportedDevicesInfo
% sudo vi SupportedDevicesInfo
And add the following after the N-Gage details:
<key>6600</key>
<dict>
<key>ATI3Response</key>
<string>Nokia 6600</string>
<key>AgendaDatabasePath</key>
<string>c:\system\data\calendar</string>
<key>AgendaMappingsPath</key>
<string>3650AgendaMappings</string>
<key>ClassId</key>
<string>5243396</string>
<key>MappingsPath</key>
<string>3650mappings</string>
<key>iSyncIniPath</key>
<string>c:\system\iSync.ini</string>
</dict>
Edit SymbianConduit_phones.plist
% sudo vi SymbianConduit_phones.plist
Add this entry:
<key>Nokia--separator--Nokia 6600</key>
<string>symbiantool</string>
All done; start up iSync and add a device. Assuming you have the phone paired, iSync will now find the phone.

