add a widget for quick access
if there is an emergency, it could be difficult to open the app to press the button. a widget (ideally accessible even on a lock screen) would make asking for help quicker. there is the issue of accidently pressing it, for example in your pocket, but perhaps make it so you have to press it 3 times or confirm that you meant to press it.
This is a great idea and we will be looking at developing it in the near future.
Thu Win commented
Kim Pitman commented
It's possible for iPhones to make a "widget" that will open a part of the app that could display a large button to hold down.