This like one of those credit cards where you get cash back?

no, it's not like credit card cashback, it will be a built-in tool on an E-commerce website to reward customers with cryptocurrencies using smart contracts. it aims at small businesses that can not spend cashback on every purchase and want to create a temporary short-term cashback campaign on their website.

So that means you need to sign up both the business and their customer, right?

it doesn't need to register any customers. It just need to register shop owner and install my tool on their E-commerce platform. I'll integrate my tool on those platforms in the near future. The aim is the tool needs zero technical config for businesses, they could easily charge their smart contract like charging any digital wallet, create the cashback campaign, and easily add the product categories to their campaign.

But if I want to collect some kind of "cash back" in crypto don't I need to have a crypto wallet or something like that?

yes, it needs to get wallet addresses from customers, whether at the beginning of the campaign or the end of it. cashback widget could get the wallet address or if the customer doesn't have any, metamask trigger for him/her.