Well its supposed to be here, but as I wrote this (not when it went live), I could not find it. However, the latest White Dwarf had the above image in it, saying that indeed a digital version of the rulebook is up for sale now.
While it says the Ipad, I am going to assume that it would follow for other platforms. Of course this is a very small advertisement in the White Dwarf sitting on the Digital Products page of the July White Dwarf.
If anyone has seen it, or purchased it, please verify it in the comments section.