The Minifon P55 was a portable wire recorder. Although all small wire and tape recorders tend to be called "spy recorders", the Minifon was actually used by the German intelligence service in the 1950s. Accessories included a microphone hidden in a watch.

The inventor of the flight data recorder or "black box", David Warner, was inspired by the Minifon Mi51, the first version of the Minifon.