Learn more about the ‘What, when, where and how’ of your customers, or your competitors customers (without ever being able to know, or needing to know, about the ‘who’ - as that would not be compliant with privacy laws).
Interested to know whether customers with your app(s) have visited your competitors? If so, where, how often, and is it more prevalent behaviour in certain regions? Want to learn whether your medium or high value customers are also medium/high value customers for your competitors? Howabout finding out whether they are more likely to shop in supermarket A, B or C, or even how often, if at all, they show up in gyms (and if they do, which ones), as a way of better understanding their lifestyle choices?