Got the "spinning wheel" functionality working during playback and record. This kind of mimics the teenage engineering tp-7. You can interrupt playback and recording, to go straight into scratching. And the wheel gives a visual indicator that's familiar to vinyl DJs :)
Fixed a bug where the scratch wheel on my tape recorder would jump on touch. Had to do with how the angle was stored and updated. Nice and smooth now.
Feel free to follow my ios app development on twitter: @radiiresearch