2020 update – Have you tried PhotoMath? Some of my Sixth Form students were checking some integration examples using this recently, it seems very easy to use and for the examples I tried looked very helpful.
PhotoMath is a free camera calculator phone app available on Android as well as iOS and Windows. To use point the camera towards a printed mathematical expression and the app gives the solution, step by step solutions are also available. Problem types are shown in the examples here and it can be a bit tricky to focus the camera sometimes, particularly where problems are very close together on a page but this is rather clever! The app supports handwriting recognition.
Experimenting, I have found that the app works if you point the camera at a screen, so one could zoom to an appropriate size first. Try these equations in the Year 7 text on CIMT for example: