Is there a 3rd-party app that uses iPhone 6's barometer?

I have an iPhone 6 and was wondering if there is any app that will simply display the current pressure using the barometer built into the phone?

Or an app, other then the built in HealthKit which tracks stairs climbed, that uses that barometric pressure for something?

Barometer++ (full disclosure: I worked on the app at Friends of The Web) shows the raw pressure values from the iPhone 6 or 6 Plus's barometer sensor. It also shows sea-level adjusted pressure to compare to weather stations around the world (using your GPS altitude), and shows elevation changes based on the barometer.

There are quite a few Apps in the App Store, including Barometer, Barometer+ and Barometer++. Take your pick. This site does the research for you.