Well, it's now available.
Been playing around with it, and it's certainly useful.
It's effectively comprised of hotlinks to every Warscroll, and you need to download them individually.
Once done, there's a crossed hammers icon that puts the relevant scroll into the 'my battle' tab. As you might expect, that means you can then access each one quickly during your game.
Kind of fun, and will certainly make rules reference easier than the pdf versions. And yes, it's free.