TAP Metronome is the first app I built for iOS, and is an experiment in minimal, gesture based UI. A single tap on the screen starts the metronome, interaction with the slider or repetitive tapping will set the metronome, and a double-tap or swipe down will stop the metronome.
The UI, and most of the metronome functionality, including tempo computation from taps was implemented during Hack the North 2016. There is a bug in the tempo timer however that causes the click track to be consistently slower than the nominal calculated/displayed tempo.
Next steps involve fixing the tempo accuracy, refining the slider UI and UI animations, and implementing time-signature selection.