I built one which stores an entry each time a user interacts, view, edits etc a entity, transaction, item. We haven't been able to glean any intel from it yet in our use case. Our initial scope was to try and identify 'issues' before they came to be a bigger problem. We thought we would see Items being looked at by multiple people when there was a looming supply problem or POs being accessed as employees monitoring critical transactions. As of today I've got 2M data points that haven't helped yet.