So I’m evaluating CompanionLink for Google as a possible tool to achieve this. Another option might be GooSync.

I tried syncing some sample contacts in both directions, with the following results:

1. Google Contacts to PalmOS Contacts

Syncing a new contact from Google Contacts to PalmOS Contacts results in the following fields being synched correctly:

• Name
• Title
• Company
• Home Phone
• Work Phone
• Mobile Phone
• E-mail (synched with the Work Email field in Google Contacts)
• Fax (synched with the Work Fax field in Google Contacts)
• Home Address
• Work Address
• Other Address
• Notes

The following Google Contacts fields are not synched:

• Home Email
• Other Email
• Home Fax
• Pager
• Other Phone
• IM Fields (Google Talk, Skype, Jabber, etc)
• Custom Field
2. PalmOS Contacts to Google Contacts

Syncing a new contact from PalmOS Contacts to Google Contacts results in the following fields being synched correctly:

• Name
• Title
• Company
• Work Email (synched with the first E-mail field in PalmOS Contacts)
• Home Phone
• Work Phone
• Mobile Phone
• Home Address
• Work Address
• Other Address
• Google Talk (synched with the IM field in PalmOS Contacts)
• Notes (synched with a combination of the Custom and Note fields in PalmOS Contacts)

The following PalmOS Contacts fields are not synched:

• Secondary E-mail entries
• Other Phone
• AIM
• MSN
• Web site

I then tried duplicating contacts to see if I could determine the primary synchronisation key. Duplicating a contact in PalmOS Contacts and then synchronising did not result in a duplicated contact in Google Contacts. However, changing the E-Mail field in the duplicated contact in PalmOS Contacts was enough to cause it to be created as a second separate record in Google Contacts. So it seems that the PalmOS E-Mail field (which syncs with the Google Work Email field) is the primary key.
Interestingly, even while the PalmOS Contacts HotSync conduit is set up to sync with Google Contacts, the syncing with the Palm Desktop still happens. Indeed, the deletion of a record in the Palm Desktop is reflected in PalmOS Contacts on each sync, but it seems does not trigger a corresponding deletion in Google Contacts (perhaps there is some QuickSync vs SlowSync thing happening here). Modifying the record in Google Contacts which had already been deleted in PalmOS Contacts (through the Palm Desktop) did cause it to be reinstated in PalmOS Contacts on the next sync.
Adding a new E-Mail field to the PalmOS Contacts record (before the existing field) causes that new field to be the one that is synched with the Google Contacts Work Email field. So it seems that synchronisation happens between the first E-Mail field in PalmOS Contacts and the Work Email field in Google Contacts, and that only one Email address is ever synchronised between the two. If there is no Work Email field in Google Contacts, then all E-Mail fields in PalmOS Contacts are deleted. Additional Email fields in Google Contacts are not replicated in PalmOS Contacts. If an additional E-Mail field is added to PalmOS Contacts, then synchronisation exits with an error on the first attempt (“Can have at most one primary email address, found 2″), and prevents other fields being synchronisedbut then succeeds on the second attempt.  As long as a Work Email field is synching properly, other non-synching Email fields on both sides are retained (but not synched, even though other non-Email fields are synched).

• Install the required kernel modules for bluetooth
• ipkg install kernel-module-hci-usb kernel-module-l2cap kernel-module-rfcomm
• depmod -a
• ipkg install bluez-utils
• Edit /etc/default/bluetooth to enable hcid and dund.
• Change the pin and host settings in /etc/bluetooth/hcid.conf, and make sure that the class is 0x3e0100 (not the default value, which is for a PDA like a Zaurus, not a “Computer” device like the Neo which can accept and route tcp/ip network connections coming in over dund or pand on the bluetooth network)
• Reboot and test with ‘hciconfig’ with a bluetooth dongle plugged in.
• Install the required kernel modules for ppp
• ipkg install kernel-module-ppp-async kernel-module-bsd-comp kernel-module-ppp-deflate
• depmod -a
• ipkg install ppp
• Edit /etc/ppp/options as follows:
  
noauth
crtscts
lock
local
proxyarp
ktune
192.168.1.XX:192.168.1.YY
ms-dns 192.168.1.ZZ

  (edit the last two lines to suit your network topology, the first IP address
  is your gateway device, the second IP address will be assigned to the client,
  and the third IP address is your DNS server)