It's not a software development kit, but there is something new today for iPhone owners.
Apple released OS X firmware update 1.1.4 Tuesday for the iPhone, saying little about the new features. The last update, 1.1.3, introduced a few new capabilities such as the ability to customize the home page, but the only thing noted as new in 1.1.4 are "bug fixes," which are probably welcome.
It's not clear at this early juncture whether the new update does anything to the legions of jailbroken and unlocked iPhones out in the world, but if you're one of those users living outside Apple's user agreement, you might want to hold off installing the update until more details are uncovered. We'll update if we hear more.
In addition, so far on Tuesday we've learned nothing new about Apple's iPhone software development kit, expected to arrive sometime this week before the end of February. It was a busy day for the company, though, with new MacBooks and MacBook Pros making an appearance in Apple stores.