This plugin is pretty simple and easy to use. Add the appropriate settings from the config-info.yml into your ~/.siriproxy/config.yml and bundle then start SiriProxy.
Then all you do is ask Siri if it's "heads or tails" and she responds with one of the two. No need to open an app or look for a coin anymore.

PS - I have some different pictures that I commented out. If you'd like to use them just switch the URL's..