Can Arduino detect a cell phone?

Hi everyone, I am new in the Arduino world, but willing to learn a lot. I am actually working on a project and here is my question: Can the Arduino detect a cell phone? And if yes how, what else do I need to get?

Basically I want to know if it's possible to make the arduino light an Led when a cell phone is in a perimeter of about 5 meters from it. Is it catching the frequency? The electromagnetic field? I would also like that the Arduino make the difference between a cell phone and all other consumer electronics (TV, radio, etc).

Thanks a lot!

Is this an assignment from school or something? Amazing how similar this question is to:


Wow! Pure coincidence. I've read the other post, but did not get everything. So, would it work even if the cell phone is not making calls? If its just turned on?

A cell which is just waiting for a signal from the basestation doesn't transmit much, just a weak keepalive. A cell which is setting up to make a call kicks out a LOT of signal, so is a lot easier to separate from all the other types of communication around the same waveband.