Let me start off by saying that we live in a slight valley. When I had a flip cell phone (with a pull out antenna), the coverage was spotty at best, but with the "chocolate bar" phones such as the Voyager and the Droid, it was much worse. Any calls really had to be done by walking outside and even down the street.
I decided to get one of the Samsung Network Extender that Verizon sells. The manager of the store I went to was so concerned they gave me a 50% discount.
I set it up by plugging it into my router (it requires an internet connection) and running the GPS antenna by the window (you can either place the extender itself there or use the 23' cable). The instructions said it would take up to an hour to find a GPS signal, but it found it in 10 minutes. All indicators were up in about a half hour.
I was expecting to see more bars, but I didn't. I called Customer Service on the Droid. Immediately I noticed that the quality was much better than I've had in the house for some time. Talking with the rep, he said that you wouldn't see more bars, but it was connected. Evidently the double tone I heard at the beginning was the extender doing its job. Very cool and good to have (in my case, at least).