File this under "it should have been free all along." Apple's "Find my iPhone" feature, previously a feature of the subscription-based MobileMe service, is now free--with a catch: it's only free for users of the iPhone 4, iPad, or newest fourth-generation iPod Touch.
That means that while many iDevices--be they iPad, iPhone, or iPod Touch--can be updated to iOS 4.2, only the most recent versions of each will get the free "Find my iPhone" functionality.
The service finds your iPhone, if by "find" you mean "get a rough GPS estimate of the location." Still,.
Its two best features are, undoubtedly, its ability to remote-wipe all data if necessary, and its triggering of a played-back sound even if the device in question is set to silent. The latter has actually saved my apartment sanity on several occasions.
Even though "Find my iPhone" requires certain settings to be activated on the iDevice in question, and, consider this: you need not fear losing your iPhone 4 under a sofa ever again.
iOS 4.2 will be live later today.