I've put this on the voting page just recently. Basically it would make the subject physically weak when triggered, so even the smallest person would be able to push them around or grapple them to tie them up. I see it as being useful to reinforce feelings of submission in a sub whose Dom/me is smaller or weaker then them, or in a person who is used to being tough and capable.
Obviously it could be just as easily made as a curse or training file, or have options where the only person the subject is helpless to is the one who triggered them.
It's had a fair bit of interest straight off, but it's now in the 'danger zone', just off the bottom of the page where potential files get ignored and lost. So if anyone is interested, please look it up and vote. My thanks, and all comments are invited.