Take the eduMIP and hook it up with the DSTR app in order to control the Mobile Inverted Pendulum from your very own cell phone!
Under $200. Single 2S LiPo battery. Readily available parts. Programmable flight control via Python.
Graphical Systems Design approach to controlling the Renaissance Robotics eduMIP with LabVIEW
An extensible low-cost open platform for learning embedded control & robotics in multithreaded Linux. Runs ROS, Python, Simulink, LabVIEW.