Here is a motor speed sensor module, the major goal is to check the rate of an electric motor. The module can be used in association with a microcontroller for motor speed detection, pulse count, ...

The hardware is consists of an Arduino microcontroller (here an Arduino Uno R3) and a pre-wired soil moisture sensor module. The soil moisture sensor module , built around the LM393 comparator, gives ...

According to [Mathieu], the answer is also yes, but only if you ignore the datasheet circuit and build this amplification circuit for your dirt cheap Doppler module.