I've been using What3words as a location indicator for quite some time. It's great for providing someone else with an accurate location and them being able to navigate to it, but it can lack a bit in some emergency emergency situations as you need the time to activate the app to find where you are and then call the police/rescue with the three words.
An app I use for emergency location that doesn't require you to look up where you are is called "Save Our Soul" SOS. In an emergency situation you get several options to depress, eg call police /ambulance etc which it does automatically and should you be incapacitated (heart attack) and unable to speak as long as you can activate it on your phone (its always an active app) it will automatically send your location to them. Other options are sirens, photos, whistles, panic buttons etc. Once activated you have 15 seconds to deactivate an emergency call should you activate it by mistake.
These 2 apps will help in just about any emergency situation except in an area where there is no mobile phone coverage ....which covers about 70% of my fishing "beats".