Notation Pad - Notation Pad is the Easiest way to write sheet music with notations on iOS/Android.
Angle Finder™ - Angle Finder™, now rebranded to Protractor+, is an app that offers a handy protractor tool on your phone.
Orpheus App - Sheet Music Reader for Android
iHandy Carpenter - An handy carpenter tool kit right on your device! There are 5 tools in this Carpenter tool kit:
Symphony Pro - Complete music notation and composition app for iPad.
Clinometer + bubble level - Clinometer+ bubble level is a handy tool that measures angles and inclinations using your device’s camera.