For the hardware side of the spectrum analyzer, [Ariel] equipped an Arduino Nano with an ADXL335 accelerometer, which is able to pick up vibrations within a frequency range of 0 to 1600 Hz on the ...

With it, via I2C, I could add an Arduino Pro Mini, and an I2C Oled Display and make a watch capable of having all this information, plus a pedometer (by analysing accelerometer data).