How to create a call back?

Hello

I recently started creating WP templates. I created some amazingly beautiful ones. However, i don't want them to be scattered around for people to get them for free. I want to know how to create a call back so whenever someone uses them, i am notified. Also, i need to know if there is a licensing or encryption method that can service the purpose.


Thanks

why not just embed some code that does a call to a page on your server that sends u a email.