Some of my friends always bring up the fact that other mobile technologies, not just GSM, have SIM cards!
They are of course correct! CDMA (verizon, sprint, telus, bell, KTF,KDDI, etc.), iDEN (nextel), PHS (willcom) all either already use SIM cards, or have the ability to use them. Of course there are a few things to note about each technology (and why I stay away from it).

CDMA - CDMA has the RUIM, which is CDMA's equivalent to the SIM. In North America at this point, CDMA has quite a lot of coverage, however RUIM is not implemented, and companies are staying away from the RUIM because it endangers their walled garden business model. What would be the point of the RUIM if you cannot get unbranded phones to work on the network? There are a number of CDMA phones available, but they are generally not unbranded and not in numerous, like their GSM counterparts. CDMA is also not as global as GSM. The only CDMA networks using RUIM are the rural CDMA450 networks in eastern europe and russia, and Three in Hong Kong (with only two phones in their line up.

iDEN - iDEN has been using SIMs since day one on their system. There is only one carrier (nextel) in the US, so the number of phones are limited. There also aren't that many global carriers for iDEN, so it's not like you can go abroad and get a prepaid SIM for your iDEN phone ;-). Motorola had made a couple of iDEN/GSM hybrids, but they haven't made any recently. It would be cool if all iDEN phones were iDEN/GSM hybrids ;-)

PHS - well...PHS is not available here ;-) It's also rarer than iDEN globally


So, yes! Other technologies have