Interesting idea....

Your Web mail account is a treasure trove of private and potentially valuable information--and thieves know it. In an online interview, one phisher claimed to make thousands of dollars every day by breaking into people's E-mail accounts and searching for messages that contain financial details.

Normally you can't tell whether you've been hacked in this way. Even if you cannily leave a juicy-sounding e-mail unread, a thief or snoop may read it and then return its status to unread. But with a little bit of know-how, you can create an electronic trip wire that will trigger whenever someone reads a rigged e-mail.

PcWorld