A bandana wouldn't protect from either of those things very well IMO. Firt aid, yes I could see the utility there for a sling or whatever but in an urban setting it should be easy enough to improvise using other materials. Signalling maybe, but any bright colored clothing would do the same thing.

Under what circumstances would you need to improvise a hat in an urban setting ?

My usual EDC list would include:

- Iphone 4 with mophie case (extra battery charge)
- wallet with ID, Cash, a couple of knuckle bandages
- Leatherman skeletool
- E01 AAA flashlight
- storm lighter with few feet of gorilla tape wrapped around it
- write in the rain pen
- sunglasses
- keys

If I am at work I may carry a Leatherman surge instead of the skeletool, a solid pair of work gloves depinding on the days activities, a write in the rain note pad and a larger/brighter flashlight instead of the EO1. Everything else I could wish for is in my locker or my truck which is'nt very far away.

If I need it and I don't have it I will improvise with what I have available to me. If I can't do that I will simply make do without.