A Subscriber Identity Module (SIM) does a lot of cool things it doesn’t get credit for. It allows you to actually connect to a network, make calls, download music, browse, chat…and lots of other stuff. I will refrain from going into details and let Wikipedia do the honors. All phones that use the GSM/GPRS/EDGE/WCDMA/HSPA technologies use the SIM to do all the cool stuff. One of the best things about the SIM is that it is removable and replaceable with another from a different carrier, thus allowing a user to travel the world and not necessarily pay exorbitant roaming charges. Much of Europe and Asia uses the kind of networks that require handsets to use a SIM card and hence makes it easy for people to invest on a cool phone and use prepaid SIM cards wherever they go.
Now Apple, being the pioneer it is, wanted to curb the rampant jail-breaking and use of the iPhone without Apple getting its dues, one way or the other. It was only a natural approach to protect what is probably the most profitable single product of the decade. Thus entered a sibling of the SIM with the iPhone 4 (and subsequently the iPad), the microSIM. To be clear, the microSIM is an ETSI ratified and designed entity but didn’t attain legitimacy of use with mobile phone manufacturers until it was embraced by the iPhone 4. There are a lot of hacks to circumvent the iPhone 4 microSIM issue
And to kick it up a notch, there are rumors floating around that a popular SIM manufacturer Gemalto and Apple are collaborating on a new kind of SIM. This is supposed to be embedded entity taking away the need or means to swap SIMs. Apple and Apple alone would control the carrier the device can connect to and make it well, interesting for hackers and jail-breakers. For now, this report is only a rumor but if it were to be true (gigaOM is fairly well reputed and doesn’t make stories up for the sake of traffic) it would give the industry a new way of locking a customer up and make it harder to jail-break the handsets.
As a parting note, it is interesting to see how much the mobile phone industry has been and is being revolutionized by the good people at Cupertino. Regardless of the implications to customers and carriers, they surely have made their mark in just 3 years of being in the mobile phone business.