If you have an account on Twitter, then you simply log in with your Twitter ID, then begin tweeting your food intake and calories. The tweets are recorded as direct messages (DMs) which are private. They do NOT get sent out through your public twitter stream.
Since I'm using Weight Watchers etools to track points, I probably won't use this tool, but for those not on WW, this could be a great way to track your eating habits and calories. And it's free!
Not sure what twitter is? Watch this clever video.