It is a surface micromachined piezoelectric accelerometer employing a zinc oxide (ZnO) active piezoelectric film.
The navigation module contains both a 3-axis fluxgate magnetometer & a 3-axis accelerometer.
These can include moving imagery in the background, like floating flower petals, but there are also some variants that take advantage of the accelerometer on certain phones.
It is a very popular mobile phone for a number of reasons, including the innovative touchscreen display and creative use of the tilt sensor (accelerometer).
Your speed is monitored using a trainer mounted accelerometer (Foot Pod) that wirelessly transmits your speed.