I 3D printed the PLA parts for Otto, added the Nano and shield, piezo buzzer, ultrasonic sensor and HC-06 bluetooth module. Using the "App code" bluetooth module in Otto Blocky it all works great. My biggest issue was fitting everything (including 4 AA batteries) in the original size body. It fit, but just barely so I used the "tall" head posted by tvollaro on Thingiverse that adds about 12mm to head's height.