Measuring speed on a certain distance, in time is not that difficult. Measuring it as a rotation you will need tools to do so. Rotation measuring equipment isn’t that expensive. They are available as mechanical or optical units.
The fun was to create such a unit myself. With
It is based on a PIC18F14K50. The 1.44″ TFT screen is a small serial module I bought on Ebay. The pick up axis is scanned through a curved disc, by a IR transistor/ LED combination.
The use of tooltips makes more types of measurements possible.
And off course, it can work with different measuring units.