For proximity-based synching for free, try http://www.apple.com/downloads/macosx/system_disk_utilities/proximity.html

Combine that with a little applescript that says (this should make sure it only does it once an hour):

– Synchronize the Device

tell application “iSync”
if last sync is less than ((current date) – 3600) then
activate
synchronize

repeat while (syncing is true)
delay 1
end repeat

set syncStatus to sync status
end if
end tell

if syncStatus = 2 then
tell application “System Events” to set visible of process “iSync” to false
end if

http://www.ovi.com/ovi/app/ovi/web/download