How is that different from what Kobo does? I have a Kobo Touch (and my family have their own Kobo Touches on the same account) and I have Kobo apps on my Android phone and tablet, Windows and Chrome/Chromium browser. They all stay in sync, when I buy a book it appears on all the devices, and when I read a book on one, the others all update their bookmarks to where I stopped. Does the Kindle sync offer anything more?