Hackable STM32 based ARM RF dev boards are literally falling from the sky!
A teardown of two weather balloon Vaisala radiosondes, the RS41 and RS92.
Repurposing tre RS41: http://www.om3bc.com/docs/rs41/rs41_en.html
Github: https://github.com/bazjo
Paper on capacitive humidity sensors: https://pdfs.semanticscholar.org/0728/24b548d91516d765c4b7facdceb350d61cdd.pdf
Podcast: Download