Depends. My controller has an input impedance of 100,000 ohms. Meaning it will not change voltage on the MAP sensors signal line. I cannot speak for other devices as to IF they will impact the voltage.
Easy way to tell.. measure with a DC voltmeter or observe voltage on your ECU's dash disply.. then attach the wire to whatever you'd like to use.. if the voltage changes, then the device cannot be used.
HTH
And Ted.. thats a great question.