These work (Rating: 4 out of 5) If you have no signal to begin with it will not work. It won't matter if you add a 10 foot antenna to your phone. If you have no signal to boost it won't happen. But if you have at least 1/2 bar of signal then it should boost it another 1/2 to 1 bar. I have read another review that tried it with 2 boosters and got even better results - I am going to try that.
Does not work (Rating: 1 out of 5) I attached this to a Treo 650 on the Cingular Network. No additional signal in my home. Save your money.