Also, don't forget the data they are harvesting. From their privacy policy, they are monitoring your shopping habits and what you do before/after you look at a product. So, that will let them "support our relationships with the operators of the retail websites from which we 
provide you with information about lower priced products"[1]

Basically, this is a data-farm.

[1] http://buyhappyapp.com/privacy-policy/