Spypig

Ever wondered whether your email has been read or not when you didn't get a reply? Some mail clients provide a notification option for this, but usually the recipient gets a popup message which informs them about it. Spypig offers a solution. They have tiny images (even a transparent one) which you have to insert anywhere into your email, and they send a message to your address once the picture gets loaded ( = when the recipient opens the email). Cute.