Being that I own my house now, and that I am a cell phone only user, it might be nice to get excellent quality in any area of my house. Right now, my T-Mobile T68i does decently in most of the house, but does get a weak signal in the basement. My roomate has a T68i on AT&Ts GSM network, and gets very poor coverage at the house. So, I figure a good solution would be some sort of amplifier I could put in the house to help boost both of our signals.

Anyone have any suggestions and advice on such a device? Or is this even possible without using an external antenna jack of some sort on my phone?