Actually, the GPS system could indeed be good for safety reasons, but in the context of the 20/20 show, the dad was using it mostly to track movements of his daughter, though again this may be the least invasive of the high-tech methods used (we use the cell phone for similar 'tracking' and we expect and receive our child's cooperation in calling us when plans change, etc).
Also, while we do not read our child's IMs or e-mails, we do expect wise use of the PC and it is in a central area of our home. Thus far, this has worked well for us. We have one rule with regard to IM - all people on her chat list must be only those whom she personally knows or has gotten from a reliable friend whom she trusts.
The emphasis in our household is on communication. We have found that simply engaging in various activities together keeps the lines open.
We also have another important way of 'monitoring' our child - who are her friends and what kind of people are they? We have found thus far that she has been keeping company with fine people who come from fine families, many of whom we've met.
Two notes about what we've found in these areas with regard to jw teachings:
1. The family bible study was actually a hinderance to good communication. Our daughter felt 'ganged up on.' The discussion was so structured that it provided little opportunity for real talking. Having a book or magazine in front of you was a sure-fire way to keep from really talking.
2. The friends that proved most harmful were jw teens. We were amazed at how they'd do things behind their parents' backs time and again, and heard stories about their fondness for underage drinking, sex, and marijuana. Not all were like this, but the ratio of jws who were, compared to that of non-jw friends, was shocking. These same kids were seen and heard at the Hall regularly of course, commenting and behaving as if they were spiritual people.