As Doug's analysis states, carrying a backup map and compass is good. I have found that it is better to periodically check your location on that map and verify direction with the compass. If you don't know your location on the map, the map may not be very useful when you realize you are lost. If he had used a map from the beginning and sighted the azimuths to prominent landmarks, the GPS problem would have been evident right away.

It would be very easy to carry enough backup clothing without going over a couple of pounds. I always (summer or winter) carry a set of Smartwool long underwear. Even relative temperature changes can cause hypothermia, it does not need to be below freezing. The most miserable night I ever spent was in a tropical environment in the mountains. The low areas were near sea level, but the mountains were over 4,000 feet. It was wet and around 45 degrees F.

In winter I carry a set of Montbel outer garments. They weigh ounces, top and bottom combined, and pack small. I have tested them in sub 20 degree F weather with nothing under them but shorts and t-shirt underneath and they were very warm.

I also carry a waterproof/windproof layer that is very light and packs very small. If I had all three of those layers on, I would sweat to death if it was not below freezing. All of these clothing layers weigh about 2.5 pounds combined, and would fit in a medium lumbar pack.

A Sea to Summit sil-nylon tarp poncho is also in my bag. Light, small and easy to build a shelter with.

I am also a fan of the Blast Match. It can start a fire on paper, leaves and dry grass without tinder. But as Doug said, redundancy in fire starting is not just good, it is necessary. My favorite is the UCO or REI stormproof matches.