I figured it out. It's not a frequency coming from my Droid, it's the frequency that my FM Transmitter is putting out. I went and bought the transmitter that they were giving away on this forum (<a href= "http://www.amazon.com/gp/product/B002XQ0ZOU/ref=oss_product">Accessory Power FlexSmart Car Mount System for MOTOROLA DROID</a>), and it turns out that if you leave it plugged into the AC outlet, it continues to broadcast the signal, even when the car's not on. I went and unplugged it and walked about 30 feet from my car, and sure enough it worked.
Cool! Thanks for the update
Mike