FrSKY Normal Precision Vario Sensor monitors atmospheric pressure and reports altitude and changes in pressure.
The FrSky Normal Precision Variometer measures the rate of change of altitude by detecting the change in air pressure (static pressure) as altitude changes.
When used with a FrSky transmitter like the Taranis, you can actually create mixes that use the feedback from the vario sensor. For example, you can have your motor reduce power when you reach a set altitude point. An excellent feature for sites that have flight ceilings.
Another nice feature of the vario is the ability to connect the FSH-01 sensor hub, thus allowing the X8R receiver's to use the existing analog sensors.