Some aircraft I fly have an hourmeter airspeed switch. This is powered by an internal battery and connected to its own pitot. It only runs when the airspeed exceeds about 25 kts.
Benefits:
- Charged on flying time only.
- 50 hour checks etc. done when needed - not early if based on tacho.
Disadvantage:
- In motor gliders you get charged when the engine is off!