Computer, Cancel Last Command
Mac OS X ships with a neat-sounding feature called Speakable Items. -- supposedly all you need to do is enable a little listener program and you can start verbally abusing your computer.
At first only one in every few commands seemed to work. My attempts to issue the command "Tell me a Joke" in a progressively louder and louder voice succeeded only in providing my coworkers with irrefutable proof that my mind is as leaky as a sieve.
I thought I might have the volume on the microphone turned down too low, so I went into the Preferences to check it out...much to my surprise, the volume was actually set too high.
Once I had the volume properly tuned, the computer began to respond to about 80% of my commands -- at least as obedient and responsive as the average human, in my opinion. When I was satisfied that it worked reasonably well, I called in a coworker to show her my neat new parlor trick.
As the Law of Singing Frogs would dictate, the program would not respond while she was paying attention. When she went away, bored by the lack of response, it started working again. My current suspicion is that the microphone is sensitive enough to pick up her breathing, which interferes with the recognition algorithms.
Still, when no one was looking I could issue commands such as "Switch to Mail", "Reply to this message", "What time is it", "Log out", etc. and usually get the behavior I was after. Even when it's working properly, however, the Speakable Items seems only marginally useful.
It's missing one key feature; the ability to print what I say. Currently I can instruct my computer: "Computer, Switch to Mail. Get new messages. Reply to this message." But until I can also tell Ethereal "Take dictation," I am not likely to bother.