Theory Apps for Android

• MusicTutor SightRead Lite
• A simple app for learning to read music. The free version gives you the treble clef. For the bass clef and more functionality there is a paid for version
  
• Interval Recognition
• An app for ear training, Uses songs and games to learn intervals. It can also do scales and phrases. The paid for version has more functionality
  
• MT FretMaster
• learn your fretboard a few frets at a time
  
• David Mead Guitar Gym
• A paid for app. Simple exercises to improve your technique
• David Mead CAGED
• a paid for app to learn the CAGED system
• David Mead Chord Coach
• A paid for app for learning chords
• iRealb
• A paid for practice tool. This app provides backing tracks to play along to. Chord charts can be downloaded from the irealb website. Mainly jazz orientated,
  

Nice, thanks.

Cheers :)

gStrings is my favourite tuner app btw

^ Me too. Also, Basichords is a great app, has every chord imaginable for guitar and other instruments (it's a lifesaver for my mandolin-playing!).