Two sensors
"The pin "AD0" selects between I2C address 0x68 and 0x69." -> 3.3V

Third base sensor:
https://github.com/felias-fogg/SoftI2CMaster

Sum up and devide.

Calibration -> needs on/of switch, begin vibrates, end vibrates

Tolerance needs to be settable -> poti...

Maybe Cases to log the events. (Grades/Magnitude of variance)

Store data on EEPROM, with time...

Maybe RTC modules? Not for MK2