Bob Solow lamented that computers where everywhere, except in the economical statistics. He meant that a lot of money was spent on IT without any statistical prove turning up that it actually improved productivity. That was twenty years ago. Nowadays there seem to be some signs that IT actually improves productivity, especially in the US. Maybe it takes a while.
So far, cell phones seem to have made not much of an impression on economical statistics either and that is weird. The fact that so many people are much more often and much more directly available in an economy that for a large part depends on person-to-person communication, should improve efficiency, shouldn't it? But if it would, you'd expect a largish jump in productivity in Europe and Japan, where cell phone penetration is high and less so in the US. In reality, it seems to be the other way around.
Part of this probably can be explained by all the negative effects of cell phones. People talking too long to other people or having private conversations. But mostly I think that we haven't really learned how to use cell phones effectively. I don't mean that necesarily in an economic way. I think that the real impact of cell phones has still to come. The telephone was first thought to be ideal for transmitting music. How society will be transformed in the end by a device that enables something very close to telepathy, we can only guess.