Streak is a Google Chrome browser plugin that allow senders see when the email they sent was read. Once you connect Streak to your Gmail account, you will be notified each time someone open the email and even tell you the exact location where the email was opened. This is bad, though.
When you send an email and was read, you will see a green eye icon that it has been read. The recipient won't know that the email is being tracked.
Sounds good or bad?