Luckily, I was able to find a solution and all development is back to normal now :)
Here is how to run the iOS Simulator from command line:
$ open /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Applications/iPhone\ Simulator.app
and that assumes that you have installed Xcode under /Applications.
You can also create a script with the content above and update your $PATH variable or even create a symbolic link under your /Applications folder using the following:
$ ln -s /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Applications/iPhone\ Simulator.app/ /Applications/