With Dictation Commands on OS X you can easily launch any application you want with a simple "Launch <name of application>". To do so you need to do the following:

Open System Preferences

Select Dictation and Speech

Select On and Use Enhanced Dictation. This will now download a file between 400 and 800MB depending on your default voice. This is so your voice commands do not need to go to Apple servers for a response.

Go back to System Preferences

Select Accessibility

Select Dictation

Select Dictation Commands

Select Enable advanced commands and Done

Now launch dictation by pressing the FN key twice. Say "Launch Calendar" or whichever app you want to launch. Your spoken text will appear above the dictation icon and your app will launch. To close the dictation icon you can click Fn twice again or you can say "stop listening" and it will close.

This can be used to launch any application.