Tie Patent Application

A tie loaded with:
A 3G (or even GPRS) radio.
An LCD of suitable size.

How it works. People get the tie. The tie is location aware, and is the output of the LCD is controlled by the data received from the radio.
This network is controlled by a company who represents ad agencies.

The display can be in the form of a pepsi logo, or something more elaborate like a full video commercial.
The tie will track the location of the user and this will be stored and compared to an existing model (the model may even be live updated via camera feeds) that track population density in certain areas of the city at certain times.

The tie wearer earns some revenue by wearing the advertisement and silently, but actively participating in the promotion of the product.

Now, throw in the concept of ad revenue developed by Google. The real-time auctioning of the ad space between competitors against a mathematical model ensures maximum revenue.

So, there you have it. I will attempt an early prototype someday soon