I am looking for one for my gal because she was groped by a chikan on the train the other night. Needless to say, she was all shaken up by the ordeal and it was not the first time it ever happened to her and I bet it won't be the last either.
The problem is she did not follow the motherfucker getting off at his stop and alert the authority (the eki-in in this case) like I told her before so I doubt she would ever use the device on anyone in the right opportunity.
The other thing I have against this idea is if she ended up using it on myself.. I can't put any wrong thoughts in her head now by suggesting anything remotely close to that idea.

Thanks in advance and your expertise on this topic is welcome.