Is it like a kid screaming and paying people to shake down restaurants? Not really. The essence of the problem solved is information asymmetry. To see this, break the app into two apps -- one that simply informs you that you missed out on a deal and makes you feel bad, and one that compensates you and makes you feel better by giving you a savings.
This is a side-payment, as in Coase's theorem. You are outraged at the side-payment, but that just hides the information asymmetry under a cloak of disgust. There is no valid reason that the purchaser should not learn the price subsequently dropped -- but the nature of homo economicus being what it is no one will use the first app without the second.
This app is an application of Coase's theorem, and takes an externality (uninformed consumers are like a clean river to dump bad pricing into at a profit) and internalizes that cost by making companies pay it -- it is always better for the market if costs are internalized, assuming markets work at all.
It doesn't matter whether the company or the consumer pays, according to Coase's theorem. The result will be the same. We might invent reasons to be outraged that the company pays, but really all that has happened is a market inefficiency -- information asymmetry -- has been eliminated. Prices are less sticky and more flexible. This is good.