We are also building such a product. The core idea is: Your browser knows you best. We leverage this to display offers tailored to your browsing behavior that include a valuable user benefit without any of the information ever leaving your browser.
You can read more of how we do this in https://myoffrz.com/en/fuer-nutzer/. Plus the code is open sourced here: https://github.com/cliqz-oss/browser-core/tree/master/module....
The product name is MyOffrz and is integrated in the Cliqz Browser/Extension as "Cliqz Offers" and in the Ghostery extension as "Ghostery Rewards Beta" for German users.
