I only know a little Mandarin Clamicide but 'Shen me' at the end of a phrase/sentence is essentially "is what" where the what can be any "existence" like what, who, anything....so that could convert to 'is who', 'is it anything' , 'is who'? and connected it can be used at the beginning to say "is what" or 'who is' or 'what is' and to my understanding sometimes could be translated as 'which is'
I have heard the stand alone 'shenme' a lot also...which would be short form for ...'what did you say' or "what is/was it?
I do wonder if it would be used by chinese speakers to steer on a meter....instead of THAT (WHAT IS THAT?) perhaps just use THAT. ...or "shenme'