The built-in compass feature in iOS isn't anything new, but in iOS 7 it does have a handy new feature: a digital level. The level is great for doing exactly what its name implies, and it'll help you take more accurate compass readings, too.
iOS 7's Compass app includes a built-in level for more accurate direction readings
iOS 7's digital level isn't a feature you need to enable. It's just there and ready to use whenever the compass app is active. The level is a very welcome addition for anyone that's using the iPhone's digital compass for navigation because it's much easier to get accurate direction readings when you know your compass really is level.
To make sure your iPhone is level when using the compass, just line up the crosshairs at the center of the compass display.
The built-in level also lets you take slope readings
You can also turn your iPhone into a digital level by swiping from right to left in the Compass app. The digital level shows the slop in degrees, and the interface spins to always show you where the high end of the slope. Perfectly level surfaces show a green background instead of black so it's easy to tell when you aren't working with a slope at all.
The digital level isn't perfect. We tried checking just how level a desk surface was with two different iPhones set in the same place and one said we were perfectly level while the other showed a slight slope. Still, it's a handy tool in a pinch.