This seems to have more gritty detail

gpe-sync

I quote:

Some other tools to get data into GPE or out of it are gpe-beam and gpe-bluetooth. Both have support for file transfer using OBEX and are able to import mimedir (VCal, VCard) data.

Gpe-contacts and gpe-calendar support importing mimedir files as well as sending these files via bluetooth and infrared.

Unison could be used to backup/restore data in your user's homedir. And it has merge facilities if you are really handy with scripting. Unison can be gotten from the debian arm archive or search the web for an ipk for Zaurus which is just a repackage of that binary.

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This doesn't really reassure me. I wonder if these same features are supported in maemo environment specifically.