I've always known I needed to get more sleep and didn't need an app to tell me, but having one sure makes it all the more obvious.
Not just too little sleep, but more importantly, not enough quality sleep. Deep resting sleep. The kind your body needs to survive.
Sleep Cycle has been an eye opener, no pun intended. It measure the amount of sleep you get, the various sleep stages you go through and overall how good (or in my case, bad) of a night's rest you got.
The best $.99 I've spent in a long time.