This app was mentioned in 4 comments, with an average of 2.75 upvotes
I've always used Waves Tuner (used to be g-strings). I've never had a problem but I'm no professional. Just use it to tune my guitar. I paid for g-strings in the past and the original developer gave away Waves free to those users that paid. He explains it pretty well in the description.
https://play.google.com/store/apps/details?id=org.cohortor.gstringsng&hl=en
If you run out of time testing it, you can try the free g-strings, which this is based off of, though Waves was rewritten and to me seems to work better performance wise.
I'm quite fond of Waves
I've tried the most popular and recommended tuner apps for Android, around 20-25. I tried them with my guitar in several environments: Acoustic, electric, inside the house, outside the house at rehearsals, at gigs and even compared them to a tunefork!
Waves was the best but about a few months ago the developer dumped that project and retook an abandoned project, which is gStrings. That one is the best one I've found.
SmartChord is another good option. Besides a tuner, it has lots of valuable goodies for guitar players, like chord dictionary, scale dictionary and more.