Coffee Calculator is my first iOS app. It's quite simple, only took a few hours to make, but I use it daily and it's quite helpful if you're picky about coffee.
It helps you calculate how much coffee to add to x amount of water, or vice-versa. It also has a timer ready, set to 4 minutes, so you don't leave your coffee brewing for too long.
Feel free to build it for your device if you have a developer license. Otherwise, you can buy it on the App Store for 69p here.
Here's what it looks like:
The current icon is awful, even for me. Would be great to replace it with something better at some point. If anyone wants to submit a replacement via pull request, that would be amazing.