Accurate tuner.
It uses the equal temperament scale, more specifically the twelve-tone equal temperament (also known as 12 equal temperament)
It is tuned relative to a standard pitch of 440 Hz.
Enjoy!
Fixed at 440 and one temperament. No options, tiny Hz scale, and worst of all it both spits out random sounds and freezes on my LG G2. Lifehacker tells me this usually sells for money which is atrocious