An Arduino based substitute for the venerable TrackIR.
 

https://www.tindie.com/products/movs...otion-tracker/

https://www.kickstarter.com/projects...motion-tracker

Features:

3 Axis Rotation Tracking (Yaw/Pitch/Roll);
Compass sensor integrated, zero-drift in Yaw;
9DOF IMU (MPU9250) + Barometric pressure sensor (BMP280);
Arduino processor integrated for on-board signal fusion, and customized application development;
Direct talk to games - USB Joystick Emulation;
And available at 65$. Not bad looking at all.

Engadin.