I once asked the Captian of the Pittsburg Fire Department what the most important things needed in a medical emergency. 1) We have to be able to find you. 2) Keep the person warm.
Salty dog, I carry a sleeping bag very similar to the one that you posted except it is for two. If truly stranded, body heat from another person may be life saving.
I also carry the "space blanket" that has grommets so that you can make a tent or a wind breaker out of it. Bungee cords may be helpful to secure it.
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What's in your bag?