When musicians have to learn a fast, difficult passage, they usually start at a slow, easy tempo and then gradually accelerate. This approach requires you to stop, take your hands off your instrument, adjust the speed of the metronome, and restart playing. Also, at high tempos, even an increment of 1bpm might be challenging. +tempo solves these issues. Beat after beat, an original algorithm will gradually increase the bpm by an imperceptible amount, allowing you to learn to play the piece at hand at your desired tempo. Just set an initial BPM you are comfortable with, your target BPM, and the total time of your training session. +tempo will linearly increase its speed over the period of the training session with impressive accuracy.
Currently not for sale (it might not work on the latest iPhones and I need time to debug it).