Being wired-up" used to be shorthand for being at the cutting edge, connected to all that is cool. No longer. Wireless is now the only thing to be. The technological explosion is even bigger than the mobile phone explosion that preceded it. And, as with mobiles, it is being followed by fears about its effect on health - particularly the health of children. Recent research, which suggests that the worst fears about mobiles are proving to be justified, only heightens concern about the electronic soup in which we are increasingly spending our lives. Sir William Stewart, the man who has issued the most authoritative British warnings about the hazards of mobiles, is becoming worried about the spread of Wi-Fi. The chairman of the Health Protection Agency - and a former chief scientific adviser to the Government - is privately pressing for an official investigation of the risks it may pose. Health concerns show no sign of slowing the wireless expansion. In the past 18 months 1.6 million Wi-Fi terminals have been sold in Britain for use in homes, offices and a host of other buildings. By some estimates, half of all primary schools and four fifths of all secondary schools have installed them. Whole cities are going wireless.