Apple outlines several embodiments of the system, but the most compelling are the first two. Long story short, they describe how it could be possible to change your plan and even carrier (hardware-willing) right from your phone. A device could store different price plan options as identifier values: once you chose one of those values, the correct carrier configuration kicks in. Imagine being presented options for T-Mobile and AT&T — if you chose the identifier for a 450 minute AT&T plan, the phone would automagically be set for AT&T service.
The patent even takes the concept further by introducing a ranking system, in which a mix of identifiers would determine which carrier config is enabled. Going back to the previous example, if you decided that you wanted a low number of minutes, and a high data cap, the device could select whatever plan would be the best fit and configure itself for that carrier.
Another embodiment of the system deals with international use. A iPhone loaded with the right carrier configurations could start off in the U.S. (AT&T), hop on a plane to Canada (Rogers), and make a connecting flight to Spain (Movistar). At each step of the way, the iPhone could easily be configured with the correct data and MMS settings, making for a seamless usage experience.
It should go without saying that this may not make it to a working phone. While I’d love to see a carrier-agnostic blank slate of an iPhone, Apple seems to have a penchant for patenting really cool ideas and sitting on them.