npm install -g yeah-cli
yeah emulate (optional <device-name>)
This tool allows you to open xcode's iOS simulators without having to open xcode. 'Nuff said.
This does not work on some older versions of Mac OS due to xcode incompatibility. Anyoe who knows why the UDID of iOS simulators does not match up is welcome to open a pr or issue. If you're on windows, you're on your own.