I had to use wikipedia to even (sort of) understand what you were selling.
I agree, too, the target audience might not know what a dead man switch is nor do you want them to think this is a last resort and literally only useful when they are dead. I'd market it as a "fail-safe switch" or "silent alarm." Maybe change the name to "Dead Spell Man" which sounds like something a non-English developer might call hang man and diffuses the "I want to kill my husband" kind of connotation.
Otherwise, the idea and intention of this app make it a really, really worthy thing to put out in the world.
There are millions of other innocuous games whose names don't invoke death, men, capital punishment, gallows, prison, nooses, lynching, strangulation, hanging, suicide, murder, etc. For God's sake, pick one of those, instead of "hangman" and "dead man's switch".
Might as well call it "Kill My Abusive Boyfriend".
The whole point is NOT to be obvious when an abusive boyfriend looks through all the apps on your phone.
Hangman's not even a plausibly amusing game. Who even plays hangman on their phone?
How about "Pokemon NO!"
Since I’ll bet your target audience doesn’t already know what a “dead mans switch” is, you get a chance to come up with a better targeted term.