Couldn't figure this one out. Definitely sounds awesome:
Syncrify is fast, incremental, and cloud-ready backup that implements the rsync protocol over HTTP.
I was optimistic about portability as it includes its own JRE and a way to install and uninstall the program service (which of course requires admin rights). Evidently it builds in a web server for its interface that the program tries to start at install, but I just got a 404 on that so dead-end.
Also, with Apache and a JRE, its also huge -- takes up 153 megs uncompressed.