They did specify, when you leave the building, however large an area that may be, they can't give completely accurate numbers since the building is not uniform in size, it may be 1000ft wide by 500ft in length. As DM eluded to, they'll probably place multiple units around the school to cover a specific area. The example of the laptops is irrelevant, it has nothing to do with this technology and how it's used.
Also, you have an obvious distrust of the media, so it shouldn't be hard for you to accept that they are trying to build this into something it's not, all they had was one family to interview, which is why they say in the report, "at least one family," because they are the only ones to have complained, otherwise you can be sure they would have had statements and interviews from other parents or students.
I'm taking what information is available right now and basing my opinion on that. I'm not adding "ifs" and "maybes" to support my case, i'm using the facts that are there right now.
How can this be about receiving more money? It's no doubt going to cost a considerable sum to set up and maintain this system, so where does the profit making come into it exactly? This helps them save money they already have, which in the long term would pay for this system and then go on to free up funds for more important, educational, things, but it does not create extra income.
The system may be open to abuse, but everything is open to abuse; let's ban camera/phone use in public, as that can be abused, lets ban Youtube, that can be abused, lets ban TV, that can be abused, the computer you're using right now, we could go on forever. It's a win/win situation, it helps keep students safe in times of need and it helps save the schools money. I see no reason to think otherwise.