My friends and I have made a mobile modeling tool for Minecraft. It is called Makerspace for Minecraft and is available in the App Store.
You can use our intuitive tools to create grand structures in minutes, that would take days to create in-game. When you’re finished, you can export it to Minecraft and start exploring! Exports both to Minecraft (Pocket Edition) and Java. Your creations can also be exported to 3D printers (.OBJ and .STL) or be viewed in augmented reality.
We will (hopefully) be releasing the Android version this summer, and are continuously working on improving our tools to make them even more intuitive. So we'd really love to get your feedback ^^