Check out the “Let it Snow” Xmas 2020 Group youtube project!”
You may also find useful this video comparison I made of of the gStrings app with Cecilio and Sabine tuners:
You can see that the gStrings app is pretty accurate (at least on my HTC Incredible phone) when compared to two "real" tuners. The Cecilio tuner that comes packaged with their violins is pretty decent, too.
Also, that's really interesting, if it's accurate, that a violin can produce almost double the frequencies that a guitar is capable of?
I've started playing violin about a half a year ago (adult beginner...), and because I was unhappy with all the Android tuning apps out there, I've created my own:
I keep improving it; obviously it works best with my violin - but hope it'll work for you too. It's free, I'll be glad if you try it out.