I forgot to mention that the circuit will be battery powered with the need to work for a long time. Say for months. MCU will be in sleep and when shaked, an interrupt wakes it, does its magic and goes back to sleep as a good kid.

Thanks for the moduleidea, it is a good but is very expensive for this project. The target price per device is about 7-10 euros max.

So for now, I'll stick with the mechanical sensors.

Ioannis