I came across this service via Lifehacker that lets you control your Mac via Twitter. It grabs screenshots for you, tells you what your IP address is, starts torrents remotely and can shut down your Mac, amongst other things. It is recommended you create a separate account for this and protect the updates, unless you want anyone to control your machine.

I gave it a quick test to see if it actually works. I just had to; and these were the replies I got:

So it passed the test but I don’t think it something I’d use because my Mac goes home with me. Best if you use one at the office and forget to logout or need it to perform certain tasks, which can be found here with a list of commands.