[JohnFen]

I wouldn't, simply because I'm not actually interested in individualized estimates of life expectancy. As far as I'm aware, there is no way to do this while maintaining a usefully low margin of error.

I'd be more interested in a general estimate of how healthy my lifestyle is (which is what I think people are generally, and mistakenly, using "life expectancy" as a proxy for.)

That said, any such application like this comes with pretty hardcore privacy implications. I wouldn't be comfortable giving that level of detail about my life habits to any unknown entity for any reason. An application that runs and processes everything locally and never communicates with an external server would be interesting, though!

[Livaton]

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)