inspirARTion is a free Google app that I have fallen in love with.
You can download it at the Google store.
I love that this app is designed for helping students draw images using the lines of symmetry. You can select the horizontal line of symmetry, the vertical line of symmetry or several number of multiple axis' for radial symmetry. The students love creating with it and I love seeing what they do. Here are a few projects we have done with it.
You can check out lessons we have done on artsonia: