GrapheneOS provides users with the ability to set a duress PIN/Password that will irreversibly wipe the device (along with any installed eSIMs) once entered anywhere where the device credentials are requested (on the lockscreen, along with any such prompt in the OS).
The wipe does not require a reboot and cannot be interrupted. It can be set up at Settings > Security > Duress Password in the owner profile. Both a duress PIN and password will need to be set to account for different profiles that may have different unlock methods.
Note that if the duress PIN/Password is the same as the actual unlock method, the actual unlock method always takes precedence, and therefore no wipe will occur.
I was kinda being facetious, more of an F U finger than a serious suggestion.
In all honesty, I can’t see how this would be useful - either you’d have to use a finger that wouldn’t look natural, and give the game away, or use a thumb or index finger and constantly have to re-load your phone due to accidentally wiping it!
If we get blessed with fingerprint readers on the back of the phone again, you could easily use inconspicuously any finger on your hand you want.
Perhaps for a fingerprint duress mode it simply shuts the phone completely off requiring the password. That would be reasonable middle ground. It’d be annoying when you get it wrong, but after a couple minutes you could get your phone back