you would need a feed from the owner of the closest cell tower of all the phones in your area at any given time.... not likely to be inexpensive if it's legal. not likely to be legal, unless you are some government agency... if you were a government employee, and could get such information, using it for advertising would be unethical...... it would also be a form of spamming, which is not only unethical, but downright despicable, and as nigel said, likely to get your teeth relocated.....