Windchill

Available on the App Store

Features

Dead simple design
Supports US and SI
Selects unit system automatically based on locale
Shows the current conditions
Tap current conditions to set calculator to those values

Neat tricks

Use babel-plugin-transform-inline-environment-variables to inline process.env.VAR. Super useful for enabling features at build time.
Add support for environment variables in .env by adding [[ -s "../.env" ]] && source "../.env" to Build Phases > Bundle React Native code and images in Xcode

App Store Release

Update changelog readme
npm version VERSION
Archive and upload
git push && git push --tags

Copyright

2016 Nic Haynes