I'm always intrigued by Twilio hacks. I'm always intrigued by APIs that work in the 'real world' or have physical outputs - i.e. not just web apps talking to ea

I'm always intrigued by Twilio hacks. I'm always intrigued by APIs that work in the 'real world' or have physical outputs - i.e. not just web apps talking to each other. Are there other examples of APIs like this? (e.g. MOO for printing)