Why would you want to use your Twitter feed as a signature?
Easy - to let all your forum friends (as well as your Twitter friends) know what you're thinking about, and what you're up to.
There are a variety of styles and sites you can use to generate a (near) instant "status" signature to use on your Delphi Forums.
Since you're using someone else's images (and presumably bandwidth) to generate the "twitsig" though, none will last forever.
Big caution here: twitter signatures may delay post downloads. If there's a problem with the source site, or if it slows down, it could slow down every page where your signature appears. Keep a close eye on it, and if you notice slowdowns, dump the sig and go back to a static signature image for a while. The last thing in the world you want to do is annoy your forum friends with delayed downloads!
Here's the first one, Twitter Signature Styles, currently displaying 11 different styles.
If those are too cute for you, or if you prefer seeing your entire 140 character tweet, try another service like TwitStamp. 18 different styles, and all a bit more reserved.
Tweetyoursig links to your Twitter page rather than to their site. In reality, that's what you want it to do, since your whole point in using it is to point people to your Twitter feed and/or forum.