Apple has enabled beta testing of Find My Mac to registered OS X developers, according to MacRumors. Just like Find My iPhone, Find My Mac allows users to locate their Macs from any web browser or iOS device. When found, you can choose to play a sound or send a message on the Mac; you can also remote lock or remote wipe the Mac. However, remote locking and wiping will prevent you from locating the Mac again.
The Find My Mac feature will be free. All you'll need to use it will be OS X Lion and a free iCloud membership. iCloud is expected to debut this fall, and we'll likely start hearing the first Find My Mac success stories soon afterward.