I find it useful taking notes at talks and lectures. Typing out notes on a phone however is frustrating and can look as if I am not listening. Lots of people like writing notes, myself included, but over time notebooks are filled up and thrown out.
Your phone can take photos of the notes but it might take some work organising them in the phones default photos app.
Below is a rough concept of an app for keeping written notes recorded digitally and organised easily.
Prototype of navigating notes