For any GPS to 'communicate' with another GPS would require:
Your position ro become a floating waypoint.
This information is somehow uplinked. How do you propose to do that?
The information is downlinked. How do you propose to receive it?
The information is displayed. For it to be of any use, it would require a rapid refresh rate.
Now think about the bandwidth needed for several 'GPS' transponders to do this.
Or just LOOK OUT OF THE WINDOW!