Do you track email delivery and opens? If so what software do you use...

Hi everyone,
I am currently working on a service to track email delivery and opens with no configuration or plugins required. You will be able to use this service straight from your email delivery window.

I'm just wondering what kind of software if any do you use?
If you don't want would entice you to use something like this?
What are stand out areas that could be improved?
Im also struggling to think of a pricing structure. Whether to base it around emails sent or maybe just an unlimited fair usage package?

Look forward to hearing any feedback.