Q:

How do I know which products have seen other customers when they took a look at the product that I am currently looking?

I am developing a website with the Drupal Commerce module, and my customer wants me to implement a functionality to allow the purchaser to know which products have seen other purchasers/customers when they saw the same product he is currently watching. 
Do you know if any specific module for Drupal Commerce is available, or can I use a combination of modules that have nothing to do with the Drupal Commerce module? 

A:

Yes the feature you are asking after is this module.
Commerce Recommender
:: Updated, Here is a tutorial on how you can achieve what you are looking for 
Drupal Commerce recommender tutorial

