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 very easy to navigate through and control. Unfortunately, I'm not much of a musician. I tried to strum along on my guitar to a few of the beats, and it sounded all right, but you'll need to really know how to play in a group to make the best use of this one.
The app itself is only US$0.99, though, so if you have any inkling to use it, it's probably worth the buy. Extra track packs are 99 cents via in-app purchase. You get about 15 just with the basic buy, and that's enough to play around, unless you're really interested in playing a certain type of music. And of course the audio can go out via the iPhone's standard jack, or via AirPlay, so there's a few ways to get it where you need it to go. Beats+ is a solid tool for any practicing musicians, available on the App Store now.