Those four items would all be great if one of the potential threats you see is a building collapse (due to weather, mad bomber, etc.)  But I don't see the bandana as being a routine requirement everywhere.  Maybe not even the whistle.  Flashlight and knife - yeah - I agree on that for sure.  Those two items I use multiple times every single day.  Not even requiring an emergency for me to need them. 
A whistle is very light with minimal bulk.  While I don't use one often at all (most commonly to get someone's attention at the range) it's worth it to me to carry one all the time.