I was able to get the Measure app somewhat to work on iPhone6, but can't reproduce it right now.
What did I do ?
There was no icon for the app anywhere. In Spotlight Search, it offered me to Open it in the App Store where it said "feature not available on this device". Fine.
Next I went to Settings / General / iPhone Storage, and found Measure listed. I offloaded the app, and suddenly had the app icon with the cloud symbol. I tapped the icon, and like with any other app, it went through "waiting", "loading" and "installing", except for that at the end, poof, the icon vanished. At some point then, I was able to see the app in Spotlight search, as installed app. When launched, I had a grey-white screen with two tabs, "Measure" and "Level". Tapped on "Level", and there I had the Level functionality back. I tried to kill the app (double tap on home button, and swipe up), but instead of a smaller image, the home screen just dimmed. I was able to repeat everything, from launching the app, to at least using Level. Next I restarted my phone, and in Spotlight Search, it now only offered me again to open the app in the app store. This time, offloading and reinstalling the app, didn't allow me again to use the app, but just opening it in the app store.