Sounds very similar to something Austin Meyer (creator of x-plane) implemented a few years ago called Xavion: http://xavion.com/

This is an ipad app that calculates a best glidepath to the best runway and guides you to the runway safely. It's intended for emergency situations when you lose an engine and quickly have to decide on an airport/runway. However, it sort of snowballed into an app with a lot of situational awareness features.

But he actually experimented with hooking that up to a plane at some point to create a self landing system: https://www.x-plane.com/2014/07/xavion-brings-a-real-world-a.... Not sure if he ever shipped that feature. I imagine there might be some certification hassle :-).