One day my dad and I had a conversation about financial things and he told me he used to always calculate the inflation-adjusted present value of past-value Rand currency in his head.
I figured why not create a very simple app to quickly and easily calculate the inflation-based present value without needing any mental calculation? So I built it over a weekend and released to the Play Store and today ~110 people around the world still use it on an occasional basis, of which I'm quite proud actually (I know it's not a lot, but this is without any promotion at all).
It can be found here (4.9 rating, but I must admit there's only something like 12 reviews/ratings 😉). Credit must also go to Renier Crause who runs the site inflationcalc.co.za and made an API for me when I asked him.