Heya, I was thinking that it would be sweet to be able to replace the antennas on the controllers with a 10 or 15 foot cord that attaches to antennas. This way, one could potentially be inside their home or in the shade or something and have just their antennas in direct line of sight of the air craft. Do antenna extensions like this exist?

They do. Contact Tony at http://fpvlr.com/shop/ or join this group and search for "FPVLR" https://www.facebook.com/groups/DJIInspire1Owners/

Be careful with that. It is easier said than done. By adding cable and connectors you will have a bit of a loss in the signal. With the Inspire Believe it has a greater output than the Phantom. I state that because of the increase in distance. I would consult with an Engineer at DJI before attempting this. It has been done with the Phantoms and it caused a greater range. But, the Posts that I read did not include the addition of a greater length of cable. The cable used is of Test Instrument quality and it is expensive as well as the connectors. You could try Aces' suggestion and the folks at RC Helicam are well versed on the subject.