A great thing about being a developer is you can make apps to your liking. If it's simple and doesn't take a year to build, why not make your own?
My wife and I have been traveling extensively in the recent months, and I've got increasingly frustrated with the clunky and ugly currency converters. All I want from it is just type in the number and see the result instantly. I don't wanna be tapping input fields to gain focus, and I don't wanna be selecting stuff all the time, I just want a minimum number of taps to get the result. Would also be nice if it wasn't sore for my eyes.
So, since it's a pretty damn simple type of app, and us being a designer/developer couple, we rolled our own: https://www.billyconverter.com
And then besides happily using something that fits your needs, it's also pretty cool to see it being used by other people around the world.
What apps have you built yourself just out of a need to get something that fits your needs exactly? Why? Did you publish them on Android or Apple stores?
