this is where I installed mine, doesn't interfere with my compass at all it is piggyback wired to the compass hookup.

 

This is a compase;
http://www.thecompassstore.com/starter.html

That thing they call a cumpass in the Jeep runs on GPS not magnetic north.

 

You are mistaken. There is a separate electronic compass with a fluxgate sensor on the jeep. The data from that sensor is processed and used by the GPS to calculate position when the satellite antenna is blocked, and to position the display orientation. There are also inertial sensors used by the jeep NAV for estimating position when the antenna is blocked too. The actual compass in the dash get's it's heading information from a datastream generated by the NAV unit if your radio has NAV. But the source for the data in that stream is a magnetic flux sensor mounted under the center panel. If it operated soley by GPS, the compass would not be affected at all by a magnet or speaker placed above the center dash pad.

 

Yeah. What he said.