Today, Twitter announced an interesting new feature: you can now track any text that appears in a Twitter update.

Using this, you can track three interesting things:

• Topics: Want to know every time someone posts about your company? You can track something like "Parakey" or "WhyGoSolo" — or even a multi-word company like track Revolution Health. One downside: tracking something like "sushi" or "Iraq" is bound to result in too much traffic to read.
• Direct messages: You can also track any time your username (or someone else's) appears: track @josephgrossberg
• Links: This one is a little more flawed, but you can track when anyone posts with a particular tinyurl in it. For example, I did track http://tinyurl.com/yv9mp9 for this site. The problem is, if they use urltea or another service, or they link to a page within your site, you won't get notified.

Like all Twitter features, this one is available on your phone or IM

The interface is very simple:

• track [whatever] and untrack [whatever] to start or stop tracking something.
• If you want to stop tracking everything, send track off.
• To see what you're currently following, send track or stats.

Alas, this last part doesn't work with Twitterrific yet; you need to be on Twitter.com to see the message.