Backstory: Upsells are a part of every sales process, from McDonald's "would you like to supersize that?" to plugins and apps for ecomm platforms like shopify. Physical clothing stores like Express and Buckle lack upsells at the point of sale.
The Idea: Physical good upsell platform.
Deep Dive: You would build a platform that would run on a tablet at the cashier station during checkout for physical goods stores. Once a cashier rings up the order, based on the items they purchased, the platform would offer a product for a one time price. You could build it such that the platform would pull from a set of items that are in stock and on-hand.
The platform would integrate with the point of sales system to immediately charge the credit card used. It could eventually ping the back storeroom and have someone bring up the item.
Validation: McDonald's proved this years ago, it's surprising more companies don't adopt this sales process.
Monetization: You would charge a monthly fee for the software and you would rent out the tablets for the POS systems. You could get fancy with the fees and only take a percent of revenue from the upsell products.
Steps to Launch: I would partner with a small retail store and offer a percent of revenue from every product sold to make it a no risk situation for the store owner.