Not only does ALFI's Fire Hot Tub look like a slice of a cartoon spaceship, but its "engine" is a wood-burning fire pit. No electricity, generators, plugs, or drain connections required.
Fill the Fire Hot Tub with water from your garden hose, fill its wire basket with firewood, and strike a match. The metal coils surrounding the wire basket conduct the heat from the flames, pushing it laterally into the tub. According to ALFI, thus process can heat the 220-gallon tub to 100 degrees in about 2 hours. While you're waiting, enjoy a few glasses of bubbles from its built-in bar shelf, or roast some marshmallows over its fire.
To raise or lower the temperature of the hot tub water once heated, raise or lower the fire basket. A stainless steel windscreen panel attached to the chrome pipes keeps Fire Hot Tub soakers from catching fire themselves.