Freevario is an opensource vario that provides telemetry data to any vario based program such as XCSoar or XCTrack via bluetooth or USB in the form of NMEA sentences. It’s a custom build pcb board featuring:
STM32F405 processor
E-Ink display
GNSS module
BMP280 presure sensor
mpu6050 motion sensor
HM13 bluetooth module
SX1276 Lora Modem (for FANET)
Micro SDcard reader
Piezo buzzer output
USB-C connector for OTG and charging

SWDIO port Signal LED CN3055 LiPo charger

The firmware runs on FreeRtos and STM32 HAL drivers.

A lot of firmware features still have to be added and developed, but the milestone releases are practically usable