Sébastien Page, iDownloadBlog:
Apple recently released a tool that lets anyone check the Activation Lock status of iOS devices. Introduced along iOS 7, Activation Lock is a security feature that prevents anyone from erasing or activating your iOS device without entering your Apple ID and password first. The feature must be disabled before a device is passed or sold to another person. Failure to do so renders the device unusable for the new owner.
The tool is available here.
Related: With iOS 8, Activation Lock is now on by default.