If you are wanting to use your cell phone in the air (ignoring whatever
the legalities might be), I haven't had very good luck with it even
when I'm close to a tower unless I'm rather low -- around 400 AGL or
less... I've tried to call while in the pattern, but could not get a
signal, but once I got down to 400 ft on short final, I was able to
make the call... Of course, 400 ft AGL on short final is not exactly
the time to be making the call... What I had used was one of the
earphone mics for the cellphone and shoved it underneath my aviation
headset... Since your voice goes through the intercom and you can hear
yourself, the mic of the cellphone earpiece can also transmit your
voice... It's not a perfect solution, but better than shutting the
engine down to idle and trying to complete the call before the ground
manages to come up an smite you... grin