A developer has uncovered a way to access undocumented MEMS accelerometers in Apple Silicon MacBooks through the IOKit HID framework. The project reveals that M1/M2/M3/M4 chips contain a hidden sensor managed by the Sensor Processing Unit, which wasn't accessible through public APIs until now. This discovery opens new possibilities for motion sensing applications on Apple hardware.

The implementation reads raw 3-axis acceleration data at approximately 800Hz by targeting the AppleSPUHIDDevice in the IOKit registry. Data arrives as 22-byte HID reports with values formatted as little-endian integers at specific byte offsets. The project requires sudo privileges due to the sensitive nature of hardware access and may break with future macOS updates.

The repository includes a practical demonstration that detects ballistocardiography signals from heart vibrations transmitted through a user's arms into the laptop chassis. This experimental application showcases the sensor's sensitivity and potential applications in health monitoring. The code structure separates the sensor reading logic for easy integration into other projects.