How to Eavesdrop on a Cell Phone. Eavesdropping on cell phone conversations is easier than you might think. It often doesn't require many tools, but you do frequently run the risk of getting caught by the person who's conversations you are listening to. If you buy equipment with cash, however, they may never discover who is doing the eavesdropping.
Use a Bluetooth headset to eavesdrop on someone else's call. Bluetooth devices send signals over a long range. If you attach an antenna to a computer and have a headset inserted into your computer, you can eavesdrop on someone else's phone call.
Go to your microwave oven. Punch in a time for about a minute or so and push Start. If you place your ear next to the microwave, you can hear cell phone conversations in the area.
Place one cell phone on speakerphone and dial the number to your other phone. Place your second phone on mute. Place the cell phone that's on speakerphone in the room with the person who you want to eavesdrop on. This person will never know you're listening to his or her conversations unless he or she discovers the cell phone.
Get a CB radio and scan the signals until you pick up a cell phone conversation. You may only find a couple, or you might pick up quite a few. The closer you are to one of the people talking, the more likely you are to pick up their cell phone signal.