Hi, I've been searching but I can't find an addon that will notify a customer of important product information when adding something to their cart.
For example we have products that require Thunderbolt which many computers don't have so we want that product to give a little notification to "check that you have a Thunderbolt connection on your computer before purchasing" We find if we put this sort of information in the product info people don't pay attention but if it flagged up when adding to basket I think they would.
I failed to find such a module on marketplace. But our cross sales module allows to show related items in the "Add to cart" notification. May be it will be suitable for you