No buttons, no complications.
DIY modder, Chan, recently composed this opus of form and function, melding a small mp3 circuit board, SD card reader, cube speaker, and accelerometer together. The result? An Apple-esque, G-4 speaker enclosure capable of sensing three varieties of motion: shock, tilt, and inclination; each separate motion allowing for control of playback (next/previous song), volume and power.
There's no word yet on a manufacturer creating one of these yet, but I would certainly encourage Chan to get cracking on an international patent before someone rides the wave capitalism off of his hardwork. Then again, Chan fully discloses how to make one of these puppies on ELM. Selfless? I think so.