Every now and then somebody writes a piece (such as the one Brian referred to the other day) which talks about "Some pestilential scientist has invented a device that allows parents to trace their child's location via his mobile telephone" or similar.

Now it actually isn't actually scientific or technical issues that are the issue here, for mobile phones are tracking devices by their very nature, and have been since their invention. You see, if you call a mobile phone, then the phone has to be made to ring. In order to be able to make it ring, the network as to know where it is. And in order that this be so, your mobile phone network is tracking you at all times. It isn't tracking you that precisely, but with sharing of information between networks (which they do, in order to track down mobile phones and sometimes to cooperate with the police) it is possible to track the location of anyone with a mobile phone to within a couple of street blocks. In terms of tracking the person with the phone, although the technology can be improved to track movements more accurately - particularly by putting GPS devices or similar into phones, in some sense it is good enough already. In this case the issues are not so much technological - the technology is already there - but regulatory and legal. Just how much of this information will be logged and stored. Having a database recording everywhere I have been in the last five years is different from being able to record where I am now on demand. How much of this information may or must be shared with government and law enforcement. And how much of this information may be used commercially and in what ways. Is it appropriate to provide a service to parents that allows them to track the movements of their children? (Certainly if I was a teenager, I would find it pretty rough if my mother was tracking me at all times).

But, of course, technology is advancing. Reading this article suggests that things are going to get far worse. Before too long we may have so called "passive radar". Essentially the point of this is that our mobile phones are throwing lots and lots of radio signals around all the time. These signals are bouncing off things, being partially absorbed by other objects, and similar. If our phones and base-stations record signal strength, signal direction, gaps in the signal, doppler effects, and other such pieces of information, it may be possible to essentially construct an electronic map of the terrain that the signals are travelling through. Essentially if you are walking down the street not carrying a mobile phone or any form of electronic tag, it may be possible to track you using the mobile phones of other people in the street. Unlike conventional radar systems, this type of tracking cannot easily be detected, as it uses radio signals that have other purposes and are there already. The privacy implications of this are, of course, worrying.

Even if this particular means of ubiquitous tracking does not come into being, or at least not quickly, some technology that achieves essentially the same thing is going to come into being at some point, like it or not. If we want to attempt to establish rights to not be tracked, or clear laws as to how such information can and cannot be used, we need to do so now, when tracking is possible but not ubiquitous. Trying to do so so after it becomes ubiquitous is going to be too late.