The easiest way to implement that would be using a Crossfire Diversity Nano receiver [1] with a backup battery. It supports GPS out of the box, directly connectable to the receiver.

For a custom solution, ExpressLRS [2] is an open source system that can be flashed to FrSky R9mm receivers that you can hack on to add features you want. Or buy Semtech [3] and ESP32 modules and build your own hardware to maximize transmit power (standard hobby receivers only have 25-40mW telemetry)

PS. TTGO LORA32 modules [4] already have ESP32 and Semtech module assembled, only need flashing (again, lower power than a dedicated 30dbm module)

[1] https://www.team-blacksheep.com/products/prod:xf_nano_div_rx

[2] https://github.com/ExpressLRS/ExpressLRS

[3] https://www.aliexpress.com/item/1005002116232826.html

[4] https://www.aliexpress.com/item/4000010599226.html

Thankyou! I've been having fun with ToWL[1] but this might be the next step.

[1] http://www.phreakmonkey.com/2016/08/towl-telemetry-over-oppo...