I've added a servo inside my TX16S. It is used as a physical gauge that can "display" any value you want:

• altitude
• battery voltage
• vertical speed making it an haptic variometer

This thing is the servo mount
The entire project can be found on my github page : https://github.com/aeropic/TX16S-servo-gauge-mod

see it working: https://youtu.be/M6sp2K4ucxU