Chordial

Chordial is a complete guide to scales and chord charts for guitar, banjo, mandolin, ukulele and bass guitar. Every possible chord can be displayed on every instrument, in any tuning. 
Tap a note to show and play the chord or scale. The fretboard can display both right- and left-handed orientations. Use the Editing mode to create an unlimited number of instruments, tunings, chords, and scales.
This app does not display "standard" chord charts; it computes the note positions based on the key, showing every possible place for each note. Use this information to decide where you want to play each chord or scale.
The full application also runs on the Apple Watch, with all of the standard instruments, tunings, chords, and scales, but no editing mode. Swipe left or right across the frets to display or dismiss the menus.