Many of us walk alone in some very remote areas where not only are we probably at a higher risk of accident due to the terrain, but we may have no phone signal.
There has recently been a series of "how did they survive" programs on TV, looking at some of the miraculous survival following accidents - last night was a guy who slipped on rocks and his legs became trapped in a 'crack'. He died 9 days later. His diary showed how he had considered cutting off his legs but decided he had a better chance of survival by just waiting it out.
A second example last night was a guy up in the mountains, deep snow, freezing temperatures, he broke his leg. he managed to slither down the mountain on his back and travelled / survived 5 days, he was found 10km from his accident spot and just 1km from his car but going in the wrong direction.
In a previous programme a British guy was on business in Thailand, he decided to go for a walk 'up the hill' behind his hotel and (long story short) got to the top of the hill, got disorientated and followed the wrong trail down, he ended up totally lost and was minutes away from death when they found him a week later.
If they had had a (fag packet sized) PLB they could all have been rescued the same 'afternoon'.
Both myself & SWMBO have a McMurdo PLB, she rides (horses) and I hike, both of us in some remote places, and we also have a sea-going boat. I see it as, as necessary as a map and compass, but like insurance, "paid for but hope you never to have to use it".
If you activate your PLB then the emergency services are informed (via satellite) within 5 minutes of your position, who you are and your next of kin contact details.
For most of the UK a helicopter can be with you within an hour.
You can simply buy a PLB and register it (and your personal details, free of charge), there are no ongoing costs to ownership and for £100-£200 they are literally a life-saver.
I really don't understand why anyone would venture out into the wilds without one.
The PLB works (and notifies SAR) anywhere in the world, on Land, Sea or Air.
It just sits on my Pack shoulder strap so it is always readily available.