Wordpress button "Take care of the price of the goods"

Wordpress site.
1. You need to make a button "follow the price of the goods" Like here (right, binoculars) Tekst ukryty
2. After entering the Name and Email and clicking "subscribe", an email is sent to the author of the record and the number of subscribers to the product appears.
3. After the price change, an email is sent to those who subscribe to the product. (The price change is already in place)
4. On a separate page, you can display the emails of those who subscribe to this product.
5. Log of events in texture (date, product, Name, email, ip) and in adminka.