Unlocked iPhone 4S on sale in US

Apple US has begun offering the iPhone 4S unlocked and SIM-free, the first time the fifth-gen smartphone has been officially sold without a carrier agreement. Priced at $649 for the 16GB model, $749 for the 32GB model and $849 for the 64GB model, the unlocked iPhone 4S will support 3G HSPA+ data on AT&T but only 2G EDGE on T-Mobile USA.

However, Apple is billing the device not as a way for T-Mobile customers to get some iPhone-shaped fun, but for frequent travelers to make calls and get online cheaply while abroad. Instead of relying on AT&T, Verizon or Sprint's expensive roaming fees, those with the unlocked iPhone 4S will be able to slot in a local micro SIM and take advantage of generally more affordable pre-paid tariffs in their destination country.

Unfortunately, the roaming support doesn't extend to CDMA networks, so even though the unlocked iPhone 4S has a CDMA radio inside, users won't be able to get online via Verizon or similar networks abroad. GSM is the standard of choice in Europe, however there are several CDMA carriers in Asia, none of which will work with this particular version of the Apple smartphone.

Apple took the unusual step of confirming it would be offering an unlocked version at the same time as carrier sales began in the US in October. Elsewhere, the company has been selling unlocked models for some time, now, with a fierce grey market of exports springing up to satisfy iPhone 4S demand in countries where the handset isn't officially available.

For more on the iPhone 4S, check out the full SlashGear review.

[Thanks to everyone who sent this in!]