Track your friends without their knowledge

The strange world we live in. The all encompassing presence of technology that was in science fiction I read as a child is here, and not in much less outlandish ways than the fiction had it.

Guardian Unlimited | Science | Guardian life bad science:
I asked my girlfriend if I could, in principle, track her for a day, without telling her how: she agreed and I set the service up on her phone, in five minutes, while she was asleep. I have a map of her movements in front of me right now. It feels very wrong. And it required no technical knowledge, or 'hacking', whatsoever. That this is possible, and so easy, to my mind, is extremely sinister. I had a squabble with one of these companies on Radio 4 yesterday, and they seemed astonished at what I was saying. They promised that they would tighten up security, and think about getting better consent for tracking people's location than one response to a text message. The notion that this technology could be misused in this way had not, apparently, occurred to them. It took me to point it out to them. Who the hell am I? Nobody. Do I work for a phone company? Do I work for the government?

In that moment, I can honestly say, I felt the fear that so many people feel with technology. I don't fully understand how mobile phones work. But now I know that anybody can use them to track people, without their permission, I share that uneasy sense that everything is, somehow, out of control ...