Mancómetro ... I'd love to know the correct usage

If any -- because as best I can tell, there is no such word.

It generates zero hits in google, and it doesn't appear in any of the four portuguese-english dictionaries I checked. [Oxford; Langenscheidt's, and the on-line translators of altavista and google] ASp, could you have misspelled? or perhaps hypothesized a concept, out of an amateur's interest in psychology?