Dunno how old you are but back in the analog cellphone days I had my mom's clunky old flip phone lying around, I was 14 or so and followed some instructions off a BBS. If you put a piece of tin foil between two of the battery contacts you could get the phone into debug mode and you could punch in any channel number and just listen in on it. I lived near a freeway, so I would spend hours in the backyard eavesdropping on people's conversations as they drove by and faded in and out of range. You had to be quiet, because if they were close enough to pick up your signal they could hear you too. Dudes arguing with their wives, drug deals, it was quite an education. The shortwave radio receiver my parents bought me as a birthday present gathered dust in the closet.