It would be great if we could access the SAT practice exercises, rather than just the videos, on the app. The scratchpad available on existing exercises on the iOS app is very user-friendly - there's lots of space to work out problems, the undo and erase features are handy, and there's a variety of colors to use. Being able to utilize that awesome scratchpad would be great for both math and reading SAT exercises. Completing math practices would be much easier, and as another user requested, the scratchpad could allow for annotation on reading passages.
I just want to add that the app is really well designed and runs flawlessly on my iPad Air. Hopefully this suggestion will help make it even better :)