They both depend on Verizon Wireless' ability to accurately measure how much data each individual customer's phone actually uses.
It should be no trick, considering the number of usage meters and traffic monitors all the wireless carriers built into their networks to make sure they could charge each other for every second of roaming connection from customers outside their normal calling areas.
That doesn't mean it will be accurate.
In March AT&T had to placate a lot of customers and mouthe a lot of insincerities to reassure people it was billing for data volumes that were as much as 4,700 percent off what the customers themselves measured at their router.
That was on a wired connection, though.
Wireless is much more predictable and controlled, isn't it?
Although AT&T was accused of overcharging by as much as 300 percent on its wireless as well.
That was AT&T, though. Not Verizon.
Verizon Wireless is famous for going out of its way to provide extra pricing services for customers; like setting up their phones so customers would be able to pocket-dial a data connection several times a day and be sure VZW could bill for it.
I'm sure there won't be any trouble with measuring data usage on wireless connections.
Just in case, you might want to check into your other options. Here is Consumer Reports' rundown. There are plenty of others online as well.
Just in case, though, you might want to look into apps that run on the phones themselves to count the packets that go in and out – rather than in your data center or Verizon's.
Just for laughs. Or verification. Whichever.
Here are a couple of examples:
Windows Mobile: SPB Wireless Monitor ($19.95) Android, iOS, Windows Mobile and most other things.