antdickens
I am not aware of any "ready to use" package or system.
You could use rsync over ssh which would probably be faster & more efficient than the vpn method, & could be automated easily enough.
For example Affa & rdiff backup use rsync over ssh, so you could examine the scripts they use for ideas.
There was a fallback/failover system created many years ago for sme5.x, it only got to draft stage AFAIK, see this link for the old howto
http://distro.ibiblio.org/smeserver/contribs/rmitchell/smeserver/howto/High%20Availability%20How-To%20for%20Linux%20Mitel%20SME%20v5.htmA few years back there was further talk in these forums of how to use more modern software tools to achieve a live fallback/failover system. I think it was using zen (?) & heartbeat etc, search the forums. AFAIR it was never fully developed, but maybe it just needs someone to do all the work of bringing the pieces together.
If you search for references to the old howto, it will probably lead you to the more recent stuff.
Try searching forum on
high availability
& also on posts by (but not limited to)
RequestedDeletion
Also Google
zen high availability