StorageStatus keeps you informed of when your internal and external drives spin up and spin down, when devices have been connected and disconnected, and how long drives have been active or sleeping. It’s designed to be a modern replacement for Apple’s SpindownHD utility, making it useful for monitoring power consumption when mobile, or diagnosing why hard drives might start up when they’re not supposed to. The app is $0.99 through February on the Mac App Store.