Agreed, nobody can calculate an individual's exact future life duration. Interesting second point - my thought is that life expectancy is actually correlated with how generally healthy our lifestyle is (positive habits for life expectancy: exercising, unprocessed diet, etc. negative: smoking, obesity, pollution exposure, etc). Definitely data privacy is crucial with any apps collecting personal data - I like your point of trying to build something that runs fully locally. (in case you want to test the initial version: www.livaton.com - the landing page calculator runs the calculation in frontend)
