Now, first off, that article is crap. I don't know if they're going to be considered "on parole" for twenty years, or if after parole, they still have to wear the thing, which is a crucial difference, that I'll return to in a minute.
Let's start with what happens here. First off, an alert gets issued whenever they get "near a school, park or other places frequented by children". Okay- so what happens then? Do cops knock on his door and ask him what he was doing there? Do they come flying in on a helicopter, automatic weapons spraying, and kill everyone within a hundred yards? Does nothing happen? Or horror of horrors, does this get logged on the offender's permanent record?!?! Again, the article is a let down here, telling me nothing. But I've got to wonder at the waste of resources that's going to be spent if one of these guys needs to drive past a school on his way to work.
Now, I want to return to the question of "during parole" or "after parole". If you have been paroled, you might not be in jail, but you are still considered a criminal. You have been released because you show signs of rehabilitation, and seem safe enough to be in the general population- but not so safe that you are allowed to be totally unsupervised. Parole is part of your sentence; you serve parole instead of doing time behind bars because you've demonstrated that you are worthy of at least some trust.
After your parole has terminated, you are once again a free citizen, and a full member of society. At least, that's how it's supposed to work. More and more, in part because of prison over-crowding, we are releasing people who really don't belong in society yet. And because of that, we need to take drastic measures like a sex offender registry and now GPS monitors. Either you're a free man, or you're not. If you're not, fine. You'll deal with whatever punishment society deems appropriate.
But if you've been released, if you are no longer on parole, then you are a free man. Your name doesn't belong on sex offender registries. You shouldn't be wearing a GPS dog collar. Once your debt has been paid to society, your debt has been paid. Fair is fair, and either it works that way for every crime, or it doesn't work that way for any crime (and in that case, we've got a slew of other problems).
Don't get me wrong, these people are the scum of the Earth. The sentence should be severe, if only to show them our revulsion at their very existence; to demonstrate the degree we have ejected them from society. But we devise a fair and just punishment, we create opportunities for rehabilitation, and we release people only when they are capable of reentering society safely. That is justice; not this political pandering. "Sex offenders are scary, vile people. Look, I am a strong politician who will protect your children. THINK OF THE CHILDREN."