Don't some safes have alerting features?

Ah posted before read complete post.

One thing saw recently though on a Glasgow high street, is a secure cabinet holding a defibrillator, and a phone handset. Have to make a call on the handset get the code to retrieve the defibrillator.
Though requires certain amount of infrastructure.

Good question, but would you equip a cache and designate it only for certain people, rather than anyone who might be in distress?

The point of some kind of automatic notification is to notify HQ that the cache is being used and some sort of response should be generated, either a rescue or crime scene investigation. Appropriate signs are required obviously.

For that matter, the contents should not be very appealing -MRE's with flameless heaters, tarps, wool blankets, jugs of water, FAK.

I would equip the landing party with an appropriate radio, securely packaged, and a sat phone, likewise packaged (separately). Everyone would have an island map and probably their own cell phone, etc.

In my experience, you begin to get radio coverage once you are about 500 feet high, improving as you ascend. The radios carried include marine channel 16 (emergency and distress) as well as the park freqs.

Solar charging capability is a great idea. Maybe some sort of power bank?

Thiskind of operation, surf landings in the back country will probably be quite common in the future, Doing the ruotine enough times, and there are bound to be incidents and problems.

Perhaps a survival cache is not the optimal approach. Perhaps we should be thinking outside the box.

See what I did there?

The Brits use bothy shelters, NY state uses adirondack lean-to's to provide shelter in wilderness areas. You could add a well or a cache of water and have a relatively high profile, low maintenance solution.
Survival caches come with their own set of limitations-inventory maintenance, rotation of stock, and pilferage. Nothing more attractive than a hidden, sealed box of gear.

...or so I am told.

Probably against the law.

https://www.theguardian.com/global/2018/jan/26/scott-warren-no-more-death-arrested-migrants-water

That pretty much sums up everything wicked and evil about humanity.

Not against the law. The Channel islands are not on the southern border. That doesn't mean that smuggling has not occurred there...

The mind boggles at the inhumanity of someone who would deliberately destroy a water cache in the desert. I have spent some time in the Cabeza Prieta, along the aptly named Camino del Diablo, and in the wrong season,it is very rough country, indeed.

I can see it, if the primary purpose of the cache is to support/promote illegal or harmful activity. It's a matter of purpose. An analogy: I would not support cutting off a food bank that feeds the hungry, but I would support cutting off the supply lines of your adversary in a war.

Plus 1 haertig