It's an interesting core idea, but it needs to account for the path dependence of existing retailers and how ill-equipped they are to adopt something totally new.
Wastage you get through stock takes, which could be done with a camera (same tablet or a phone), cloud sync so no cradle needed
It could integrate with the latest cloud based accounting systems which their existing pos wouldn't be able to handle (referral $$$), and large companies who have a lot invested in their pos system could pay an employee to integrate it though the apis if they want the search traffic
The biggest problem would be integrating it with the cash tray that goes ding, which I think is desirable I think to stop costumers reaching over the counter and grabbing money while you aren't looking. I guess deploy it as a phone peripheral.
I just wonder if the idea itself has merit. I suppose neighborhoods would specialize more and there'd be less stores with identical stock.
The other opportunity would be advertising to those retailers by suppliers and taking a cut of sales for orders to suppliers, I think that could be where the real money is
However, my comment was directed at the parent who claimed that a business wouldn't want to use it even if the product did exist.