You can use the app to track the usage, Just like the other data addons :)

You can easily track usage in the app, usage alerts at 80%, 90% and 100% are also sent. Bear in mind voice billing is 3-4 days behind as the files need to come from the carrier partner so keep a track of your usage taking that into account. You can always purchase a second pack as back up, or better still, enable Walk off Working (if you are pay monthly) a pack will be auto purchased as required.

andyb:

 

... better still, enable Walk off Working (if you are pay monthly) a pack will be auto purchased as required.

 

This!
It worked simply and seamlessly for me going from NZ to Hong Kong, France & Germany, Canada and the USA, then back home.
No fuss, no worries