Segway	This guy's version
Safety features	Everything is dual redundant. For example, "in the unlikely event of a battery failure, the system is designed to use the second battery to operate the machine and allow it to continue balancing until it is brought to a safe stop."	There is no redundancy or backup system. It is not even robustly made. Loose wires literally dangle out the bottom. In the fairly likely event of the software crashing, a wire coming loose, a component failing, or the batteries running low, the wheels will stop and the entire kinetic energy of the system will be used to accelerate my head toward the ground.