The EDL is simply a substitute for a passport that can be used at land and sea ports only. You don't have to get one. It is meant as an optional means of convenience for those that frequently cross the border. Other options include the new passport card or a Nexus speed lane card.
I don't know whether you can really scan these from a distance or not. When you present a chipped passport or enhanced license the customs officer has to place it in a reading device.
RFID chips can be read from a distance of up to a few yards without your knowledge unless they are enclosed in a something to block electromagnetic energy.