This is not a valid way of judging RMS or his claims. He isn't complaining about the concept of a technology that allows people to talk while on the go. Rather, he is complaining about the specific implementation of mobile tech with which we're currently saddled.
To answer seriously, however, the largest effect of reduced cell phone use would be that automobiles would be much safer, for their passengers and for everyone else.
More to the point, if people - en masse - refused to use cellphones that tracked you, someone would be selling cellphones that don't. And then RMS would presumably carry a cellphone.
Just to point out a bit of an overly binary comparison: There is a middle ground here — consider a powered-off, pre-paid phone. No constant texting and so on, but also there for emergencies (in which instance, you turn it on exactly when you actually want to be tracked — by emergency personnel).
"911, 911, we had an accident because everybody in the car kept texting and facebooking during the whole ride. 911, 911, it's a good thing we have cellphones and tablets with us!"
as jessaustin remarked, "[RMS] is complaining about the specific implementation of mobile tech with which we're currently saddled."
Listening to RMS would mean that if you do carry a mobile device, that it would use entirely free software including all drivers and bootloaders, that it only communicates with other hardware running entirely free software (i.e. only basetowers or wifi routers running free software), and that all the internet services accessed ran entirely free software (e.g. private email servers instead of gmail, pump.io & GNU social instead of twitter & facebook, mediagoblin instead of youtube, wikipedia, yacy or some other free software for search, etc.
To answer seriously, however, the largest effect of reduced cell phone use would be that automobiles would be much safer, for their passengers and for everyone else.