This might seem like a strange question. Is there some sort of way for an app to launched by pressing the screen for a few seconds on touch screen phones? the reason why I ask is because this would be a great feature for like a panic button. of course the app will have to calibrate to the owner's thumb to prevent accidental pressing from objects in purse or pockets.
As far as I know this isn't really possible. But there are apps available in the Play Store that implement a Panic Button where you can place a button on your home screen (and maybe also your lock screen, but I haven't it yet).
One of those apps I found is Red Panic Button. But you can also have a look in the Play Store yourself if you search for something like Panic Button etc.