Kindle _does_ support "Furthest Page Read". People have reported "problems" with it working a little too well (for example if they share an account with a spouse who has finished a book, the other user can sync to a page early on in the book because Furthest Page Read is the end of the book).
Also, the latest version of Calibre (v0.7.44) can save the proper metadata into any .mobi file that will allow Amazon to sync "Furthest Page Read" data for non-Amazon books. If you are importing a .mobi file, you will have to "convert" it to .mobi to get the extra metadata. If you are converting a file to .mobi, the meta data is added automatically. Note that you cannot customize the ASIN field (so "Book Description" menu item on Kindle, from within the book, won't work properly).