The Twist is a rather fascinating development in the increasingly crowded field of power add-ons. It can be used in 3 rather distinct ways. Firstly as a traditional power add-on with a handle bar. Next, as a powered 3rd Wheel type (think Freewheel) that connects to and is controlled by a wireless controller and phone app. And lastly, it can go under the chair and out of the way mounted closer to the axle bar.
Other notable stats are that it uses a beefy 750 W motor with a 360° rotating wheel, comes with a flight-safe battery with 20 km of range and weighs in at very reasonable 7.5 kg.