Email Notification????????????

Friends i was wondering how can we check that the mail that we have send to a person when the reciever have viewed the mail.......... i came across  this amazing site which solves our problem...........
go to this site:
http://www.spypig.com/
step 1:Enter your email address..........
step 2:Enter your message title i.e subject of the email message
step 3:Click a image which you want to track the email
step 4:Click to create my spypig....
step 5:Copy paste the image anywhere in your email message
step 6:Send the email message as usal......
U will get an notification when the reciever reads the message!!!!!!!!!!!!!