Have you considered that this could be extended into a musical rythmn training app? Eg, as somebody who plays guitar, this could be a good tool for learning to identify and play rythmns. So you could create levels that correspond to things such as number of bars, tempo, time signatures, and whether they include crotchet, minims, & quavers.

Eg, I'd like to be able to pick a tempo and sit down and work on different 6/8 rhymns. I assume this could be a causal way to get better at music.