A Teslascope is a radio transceiver that was alleged to have been invented by Nikola Tesla for the purpose of communicating with life on other planets. Even though Tesla talked about interplanetary communications on many occasions, it has never been confirmed that he built this particular device.
It is sometimes associated with the 'paranormal' Hyperdimensional Oscillator.
Read more about Teslascope: Claims, Talking With The Planets