Ajapaik android app (code on Github) enables a very easy way to align historic images with contemporary view in order to make rephotos (repeat photograps, then-and-now picture pairs).
We want to connect the app to Wikimedia Commons in order to retrieve images from Commons and also save rephotos back to Commons. Also Wikimedia-authentication would be nice.
The app is used in Finland for the rephotography track of Wiki Loves Monuments competition.