Everything you need to know about Apple's unlimited text, picture, video, location, and contact sharing messaging service for iPhone, iPod touch, iPad, and Mac
iMessage works in parallel with SMS and MMS on the iPhone, and brings the same type of messaging functionality to the iPod touch, iPad, and Mac. It only works between people running iOS 4 and later, and OS X Mountain Lion and later, so you can't use iMessage to contact people on other phones or on Windows computers, but you can use it to send and receive texts and photos, and share map locations and contacts, with anyone using the latest Apple gear. And since there's no charge for iMessage beyond data (cellular or Wi-Fi), you can send unlimited iMessages pretty much for free. Take that, carriers!