If I remember correctly, the earliest cell phones were closer to 3-5 watts. Current ones are somewhere between roughly .25 - .5 watts. The FCC generally limits SAR, rather than transmission power, because different frequencies are absorbed differently by the body. Perhaps cell phones have special rules but I would have no idea about that.

You can contrast that with handheld ham radios ("Handi-Talkies"), which can go up to 10 watts, but I wouldn't transmit at 10 watts next to my head unless my brain was feeling cold and needed some toasting.

By the way, it's not uncommon to hit repeaters that are several miles away on .5 watts VHF with a ham radio. (Note I didn't say it's reliable.) Of course, this is apples and oranges to what you're talking about because I'm referring to an analog FM transmission and you've said the Nextel is digital.