A long time ago, I wished I could have all my personal data (addressbook essentially) available in read-write mode from any of my work places (linux laptop, home iMac, linux at work), and also shared with my wife.
As this remained a itch to scratch too long, I finally decided to see how far I could solve it myself. So I've taken replication 101 (mostly followed references from the interesting white paper from the unison project), and experimented a bit in Python with simple ideas.
The result fits my needs (I can read and write from several places the system handles propagation and updates, and reports conflicts), but is still far from either complete (I still need to put some sugar on the conflict resolution procedure, to finish the Addressbook.app client,...) or polished (the implementation is certainly not space nor time efficient)
At least I feel better now :-)
BTW, if you want to play with it, it's available here:
It will probably randomly discard your data, crash your network and repaint your bedroom, but if you wish to test it, feel free.