A friend of mine runs a charity [1] that deals with providing AED (Automated External Defibrillator) devices to organisations. These things save lives. They can deliver shocks to the heart if necessary and can guide laypeople through giving CPR until help arrives (I think many models now actually tell you if you aren't giving strong enough compressions, for example).
I would also highly recommend people go through this app [2] to get some familiarity with CPR. Then take a proper CPR course (I need to take my own advice on doing a proper course, actually).
i see those AEDs popping up around, ie in the office, train station, every pharmacy around has them. My wife is an emergency doctor, an she has clear opinion about those - yes they save lives, but in most cases, people will end up as 'vegetables' (not sure what's the proper english term for +-brain death). I only presume she meant more severe heart attacks that would normally result in death prior to emergency arriving or shortly after.
So don't expect miracles where none are currently possible. Do all you can obviously in case of need, and ideally make yourself familiar with procedures a bit, any delay will worsen the chances.
Just like with old school CPR, there's really no guarantee you won't be a vegetable. Maybe you get lucky and the person doing CPR does it right, the AED arrives soon enough, and the paramedics arrive soon enough. Always make sure you have a living will to cover such kinds of situations. I would hate having my vegetable body ending up in a fight between loved ones who want to keep me alive and loved ones who want to do the humane thing.
Here in Denmark there's a volunteer "heart runner" programme. If someone calls 911 and has a cardiac arrest, people in the programme that nearby can be notified to fetch an available public AED and run to the patient (or attempt manual resuscitation).
According to their material, the 30-day survival rate in Denmark has gone from 3.8% (2001) to 10.4% in 2016, with 67.5% bystander assistance: https://hjertestarter.dk/english/you-can-save-lives though it's not clear how much the programme itself can claim.
According to various papers, rapid CPR/AED after a heart attack can triple survival rates.
It's still pretty bleak outcome, but better than e.g. in 2002 Detroit, where 1 out of 471 out of hospital cardiac arrests (OHCA) survived to hospital discharge. In USA, all those stats are apparently being tracked by a programmed called CARES.
Nah, vast majority aren't locked up here, from experience. Pubs in the UK tend to have them, as do larger shops, community halls, libraries, I've seen old red phone booths repurposed as AED storage, in Birmingham city centre I saw a really modern one like one of those light-up ad screen / phone booth / touchscreen signs, which could simultaneously call emergency services, deliver CPR advice on the screen and dispatch the AED stored underneath - was awesome. Honestly I'm surprised (and pleased) that they don't get stolen/vandalised more considering the amount that are just out there - though I don't know what you'd do with a black market AED lol.
I have yet to see one that's properly locked up [that didn't have easy to break emergency glass, anyway]. My workplace has a few in special AED boxes, but those have the emergency glass and the hammer.
Must be a southern thing. I've never seen an outdoor (or phoebox) one that doesn't have a keycode lock on it. You're supposed to call 999 before using one anyway, so it's not a major impediment.
I would also highly recommend people go through this app [2] to get some familiarity with CPR. Then take a proper CPR course (I need to take my own advice on doing a proper course, actually).
[1] https://responseforlife.org.au/
[2] https://www.resus.org.uk/apps/lifesaver/