Que. How to FM tap your neighbors telephone?
Ans. In short: "Listen in to the telephone conversation on your radio!"

But before you try this, a disclaimer:
All information provided in this post is for educational purposes only. I do not support nor encourage this monkey business. If you choose to make this device; you, and only you will be responsible for the consequences. Happy building!
Lets move on.

I had taken my old Landmine Landline (wired) phone and thought of making it a cool spy device. You know like in the Bond Austin Powers movies, only difference being, this one's a little bigger. Click on a image to "enlarge" it.

I don't have to explain what I'm going to do with this or what this is.

The toughest time I had was removing the screws. Ultimately found a fit and undid this box.

Internals: On the left is the FM transmitter and right is the original phone. And you can even see the antenna stuck with hot glue around the casing of the phone. Another trouble I had was with the power supply to my FM Transmitter. I took 5V from somewhere in the back, Very hard to find and solder to. Be very careful here, don't short anything and please for the sake of mini-me put in a 220~470 ohm resistor.

Here shown is a cheap FM Transmitter tuned at about 90~95MHz depending on distance, interference, cheapa$$ receivers and random people coming in between.

This is all there is to it. Its really simple. Can be done to any phone, just take care of the power supply to the FM transmitter and the antenna. Drop in a line if you have any Q's. ill try to answer as soon as I can.