This may or may not work for somethings but for any form of self injury I highly doubt it.
and why do you doubt it?
People self injury for a variety of reason in a variety of ways -- most of which is done in private. Do you know what it takes to trigger self injury? Sometimes the client doesn't.
does it matter what triggers the SI?
look, just this last Thursday I had a minor breakdown (since last year I have had them for causes un-related to cults). it so happened that a particular person triggered the response before boarding a bus before a bus ride of about an hour.
as it happened, he boarded the bus with me. as I had nowhere else to go except to break off my trip and did not want to break down again in front of someone I knew (before, I had hid myself before he saw me).
on the bus a woman started scolding her children and I just about started to scream.
the combination of circumstances made it so that I controlled myself. since that time I have had only one comparitively minor breakdown.
the principle works like this (think I explained it before, but here goes):
step one. brain says -- for whatever reason (again, reason or trigger irrelevant) -- "I want to, I will, hurt myself."
step two. the action does not go through.
step three. the brain now remembers the sensation of having the urge and not following through with the impulse.
For those who self-harm in a dissociative states this is BEYOND dangerous. Only one trigger could unleash an avalanche of SI which could also morph into serious suicide attempts based upon being triggered (suicide and SI are NOT the same thing).
the important part comes down to consent (the person wants to go through with this) and predictability (they know what will happen) and the fact that they have decided to do this to no longer SI.
incidentally, I have a long history with SI. however it doesn't bother me that I do it. I do it a lot less than I used to do it.