The service runs on Windows Mobile and BlackBerry devices (Symbian would seem the obvious addition). Conceptually, I'm all in favour of these kinds of packages -- precisely because they're optional. Much better to have services available for parents who want to monitor their children's communications than to force all of us to endure them.
On the other hand, as I don't have kids myself, I don't really know whether I'd pony up $15 a month for mobile phone security. So let's hear from the parents out there: is this too much? Is there a better way to get the same results? Share your thoughts in the comments.