DidTheyReadIt.com

From USATODAY.com: "DidTheyReadIt.com, which will launch Monday, allows anyone to secretly track e-mails they send. You'll see whether someone opens your e-mail, how long the recipient keeps it open - even where geographically the recipient is reading it."

I think I may know how they did it. It won't take much work to build a prototype of the same thing they've built. It'll work on Pine, Outlook, and HTTP-friendly email client. It's so simple technically I couldn't believe i didn't think of this before *<8)

It's an interesting business idea; they prey on people's insecurities.. (i.e. you want to know whether what you've sent has been read). Actually with this setup, you can do more than that, you can "recall", i.e. take back, an email before it's read, or even modify email contents before they're read. Remember the last time you sent a boo boo email ? :-]

Or do a workflow kind of system where you can send a follow-up email based on the recipients reading behaviour. This is very useful in email marketing.

For example, if your recipient took a long time to read, the guy may be interested, so your system can automatically send nother email to follow up. If your recipeient only briefly browsed through, your system can automatically send another email that's simpler, etc.

I say these guys are only touching the tip of the ice-berg, because with what they have, they can really offer a tool that revolutionize email marketing.