The Apple iPhone normally requires a two-year AT&T contract, which means that some buyers in the US have had to shell out the $175 (£85) cancellation fee in order to close their current mobile phone account down.
Of course, the lock-in also means that people in the rest of the world can't buy an Apple iPhone and stick their domestic SIM card in it in order to save on US roaming call charges that would otherwise incur.
By using software called iASign , users can make the Apple iPhone work with existing SIM cards registered under AT&T or Cingular, and possibly mobile virtual network operators (MVNOs) SIM cards on the same network. This would enable you pick up an Apple iPhone, put in your current SIM card and... well, see it work!
Contributors to the iPhone Dev Wiki website are continuing to work on a means of unlocking the Apple iPhone for any mobile operator, but report that the device is extremely well-protected, having a maximum number of unlock attempts and a unique network control key for each unit.
Any unlock hack is also only likely to be temporary - software updates from Apple are bound to seal any hacker-friendly chinks in the iPhone's lock-in armoury.