What's preventing that is the phone needs to communicate with towers. There's
no way around that.
You also can't hypothetically work around the problem by connecting via some
other phone network because people communicate with you in a way that
requires your phone to identify itself (each phone having a unique number
assigned to it). The only way around that is a fundamental change of how
phones work to the point where you might as well just use the Internet.
RMS expressed in his talk at LibrePlanet an idea to use a parabolic antenna
that is pointed to just one particular tower, preventing triangulation, but
there are problems with that. Most notably, unless you're in an area you're
familiar with (such as your home), there's no way you're going to know where
the various towers in your area are. There would have to be some way to scan
for towers for it to be easy to use, and doing this just once would be enough
to possibly infer your position. You also wouldn't be able to move as easily,
since you need to keep pointing the antenna at the tower. So basically, this
would be something extremely difficult to do, requiring knowledge of where
the towers are and possibly some math to make sure you're pointing the
antenna in the right direction. You would be better off just going a distance
to a place you're not going to stay at long, turning a regular phone's
communications on, talking, then turning the communications off again.
In a nutshell, I think preventing phones from being able to get your position
without also preventing them from making and receiving calls is a pipe dream.
We should focus on making them work with free software so that we can be sure
of when it is and isn't communicating with towers.
