In addition to seeing a history of changes for my tracked fields on a record, I want my history to include changes to line items (i.e. added, deleted). I created a mockup for opportunity/opportunity line items, but this could be applicable to master-detail relationships for custom objects too.

If you like the idea, please add your comments on what information about the line item you want to see within the History related list on the parent record. Do you just want to see what line item has changed (i.e. Changed Product)? Or do you need to see more specifics of the line item change, on the parent record (i.e. Changed Quantity on Product)?