Damn, what a great idea! I almost couldn't stop myself from installing it!
The only problem with it is that it increases the pages size significantly. In my tests, it doubled the page size, and that's pretty significant for modem users, like myself. How about making it optional, on a per-user basis, in the control panel?
BTW: You should trim() the text before storing it in the database, and also maybe get rid of repeating spaces and line breaks. Oh, and how about previewing redirects as well?
Great job everybody!