Beats+ is a niche app, but it's probably very useful for the kind of person who could use it. It's a simple but powerful drum machine app, featuring over 50 different drum loops (frequent updates keep the library fresh) to be used as accompaniment with whatever kind of music you want. In addition to playing with the drum loops (which run the gamut from pop and country to R&B and rock), you can adjust the beats per minute tempo of each, or just hit a button to randomize everything.
The app's interface is clear and easy to use. It could have a few more options, like maybe the ability to time out different beats or somehow set up different changes in the rhythm, but what's there is