In a survival situation, urban or wilderness, you blend your knowledge and skills with available gear to surmount the challenges presented by the emergency. Threat profiles vary widely - Philip puts it very well in his post. Knowledge and skills outweigh gadgetry in the final outcome.

Get training in first aid. Almost by definition, a disaster will tax the EMS to its limits. Even when not strained, the most immediate relief for an injury is at the ends of your fingertips, guided by your smarts.

There are lots of useful, cool items out there which can help if properly used. There is also a lot of marketing hype, selling junk by the carload. Some things are useful in some circumstances, not so in others. Most of what you need is probably already at hand, needing only recognition and organization. A lot can be picked up locally at your supermarket or home center. The fun comes in acquiring the rest (I am an incorrigible gadget freak - my colleagues referred to me as "Captain Gizmo.").