Boost Mobile will be the latest carrier to be supported in the US. They join the likes of AT&T, Sprint, T-Mobile, and Verizon which is pretty much all the major carriers, as well as US Cellular. We expect that over time there will be more carriers added to the list in the US, but for now there will be six that are currently supported.
In addition to the US, Google Play Store carrier billing has also expanded its support to other carriers around the world. For our non-US readers, this includes Vodafone in Indonesia, Beeline for those living in Kazakhstan, Orange for our readers in Luxembourg, Telenor Pakistan, Telekom in Slovenia, and Vietnamobile and Viettel for Vietnam.
While this is great for bill consolidation, it also comes in handy for those who prefer to avoid using their debit/credit cards, or for those who do not own one.