During my vacation at the island of Langeland, Denmark, I found a washed up radioprobe from a German weather balloon on the beach. It is a Vaisala RS41-SGP single use instrument in a styrofoam enclosure that can measure air temperature, humidity, pressure, speed and direction. It uses a STM32F100 microcontroller as the heart of the unit, has a UBLOX UG8010 GPS chip and a RPM411 barometric add-on board. There is also a lot of other teardowns of interesting electronics here.
Not a part of the video, but it has a Si4032 ISM transmitter for the 400 MHz band: https://www.silabs.com/documents/public/data-sheets/Si4030-31-32.pdf