This really ought to be added to the documentation here:
I was confused by the post here:
because it says this:
Requires new plist parameter (“NSLocationWhenInUseUsageDescription”) in build.settings when building with the iOS 8 SDK. There is no issue when building with the public release build (2393a) running on either an iOS 7.x or iOS 8 device; on daily builds, there is similarly no issue as long as you build against iOS SDK “7.1” (not “8.0 Beta”).
Since I'm choosing 7.1 from the drop down, I assumed that meant all was well for me, but it wasn't...
Adding the NSLocationWhenInUseUsageDescription to the plist in build.settings is apparently required for iOS 8 devices, even if you're choosing "7.1" from the iOS SDK drop down in the Corona Build window. So really, it might as well just be considered required for everyone from now on, which is also why it really should be added to the Gotchas in that documentation, along with the android settings.
Also, I didn't know what that usage text was for, or what it should look like. In the end, I figured it out. It's what shows up when you go into Settings > Privacy > Location Services > Your App. At the bottom of that screen, it says, "App explanation:", then shows your explanation.
An example is the Camera app. Its explanation is, "Photos and videos will be tagged with the location where they are taken."