Unlike the others, this app actually LISTENS to the music using the phone's on-board microphone. Simply start the app, and the BPM is updated once every seven seconds. The app works best with music that has a strong beat.
Select either 60-120 BPM or 100-200 BPM to get estimates in those ranges.
Choose from either the modern or old-fashioned skin.
Switch the app into "nerd mode" to have a look under the hood. Watch as a spectrogram is generated in real-time (choose color or black & white). Below the spectrogram you will see the rate of energy change of the music. Peaks represent beats or other musically significant events. Once every seven seconds, the bottom of the screen displays a chart with the candidate beats per minute. The largest values are the most likely.
Note that the app also works on music without a strong beat, but you may have to snap your fingers, clap, or tap on the screen to the music to help it register energy transitions correctly.
For fun, try beatboxing while running the app!