kind off... but if i am reading this correctly, its more a backup than sync... and if its done "correctly" the other user wont have access to the data... ideally, all data would be encrypted at rest, so i backup my photos to a friends house and he backs up to mine, neither of us have access to the others data... sync thing does have something similar, but its not backup (if your sync folder gets crypto locked, your screwed since it will sync to the other end).
Looks intersting indeed! Still in developement but already usable. UI is only in german though.