It would be useful if KLM had an App to display the progress of bags, just like Delta do. KLM's internal tracking will be much more detailed than the pretty useless World Tracker system, so I don't see why it can't be used. As the OP said this would help piece of mind a lot; I might be in Madrid and my bags in Cape Town (this happened to me a couple of years ago, KLM Platinum Line found them) but at least I would know they are not lost.