Check out this new metronome/tuner app. Not only does it have standard metronome and tuner applications, but it has record and play back features as well. This app will show sound waves of what you play (which can aid in developing steady vibrato and correct articulation), and it has a Smiley Face to show you when you’re “in tune.” Who wouldn’t love that?
You can adjust the tuning sensitivity from beginner, advanced or professional. You can also play back notes with sounds of your instrument to help pitch matching or adjust the intonation to match equal temperament (standard piano intonation) or for just temperment (standard ensemble intonation).