According to this article BitTorrent Sync is out of Alpha and ready for use on mobile and desktops. There's also a link to NAS that run BitTorrent Sync.
I was wondering if it was yet possible to use this with the RT-N66U.
I gave up and made a separate spreadsheet for this. It's a PITA to setup initially, but it works fine thereafter.
I assign all my known devices to an IP so if anything outside that range pops up I can more easily track it down.