LightTracker is one of the most affordable, smallest, lightest, powerful and open source LoRa and LoRaWAN trackers available. It makes tracking pico balloons, weather balloons, model rockets, RC aircraft, and anything else that flies simple and easy.
It is able to report location, altitude, temperature and pressure to the internet (LoRaWAN networks such as Helium and TTN) or direct to another LoRa radio module with a solar panel/super capacitors or just 4xAAA batteries.
Because LightTracker is open source you can add your own custom sensors via I2C/SPI pins.