If you or a loved one is in a wheelchair, always have a spare tire on hand and a few tools to help you replace it, since you can't always count on being near a medical equipment store when you need to be. Lacking this option, find a nearby bicycle repair shop that will repair a tire for you while you wait.
If you've got to deal with medical equipment on a regular basis, carry a few tools along with you so you can make small repairs as necessary. Allen wrenches are particular useful, since most braces, walkers, and wheelchairs are keyed to them.