From Alexander Shtuchkin:

Code & schematics for position tracking sensor using HTC Vive's Lighthouse system and a Teensy board.

• General purpose indoor positioning sensor, good for robots, drones, etc.
• 3d position accuracy: currently ~10mm; less than 2mm possible with additional work.
• Update frequency: 30 Hz
• Output formats: Text; Mavlink ATT_POS_MOCAP via serial; Ublox GPS emulation (in works)
• HTC Vive Station visibility requirements: full top hemisphere from sensor. Both stations need to be visible.
• Positioning volume: same as HTC Vive, approx up to 4x4x3 meters.
• Cost: ~$10 + Teensy 3.2 ($20) (+ Lighthouse stations (2x $135))
• Skills to build: Low complexity soldering; Embedded C++ recommended for integration to your project.

(Github page)