The app is called Fishing Knots and after playing around with it a little bit, it is good for a reference so far. I feel it has all the major knots such as Blood Knot, Arbor Knot, Albright Knot and so on even includes knots for spinner fishing.
It seems to be on par with most instructions with minor tweaks. For instance Blood knot it says to wrap each end 5 times instead of only 4 which is what I have been taught.
I guess the main point here is that it is free and you can't beat that. It is useful for beginners as a quick guide and I think even people who are familiar with knots. Brain Farts happen to everyone so this is good for a reference for veterans. I'd give it 3.5 or 4 out of 5. I would like to see more of an animated interface.