They call it hot ice because sodium acetate is extremely unstable (probably moody and demanding too) and begins hardening immediately as it drops below its melting point of 58.4 to 58 degrees C (about 136.5 to 137 degrees F). The process is exothermic, and the resultant "ice" hot. When boiled and cooled again, the substance returns to its starting liquid form. Without forming crystals, which is part of what makes it an ideal compound for consumer items such as heating pads and hand warmers. For our purposes, it just makes a sweet chemical to screw around with.
Sodium acetate sells as colorless crystals (combined water molecules evaporate when exposed to air, so it arrives in solid form) and is soluble in both water and ether. From the looks of the video and photos, I'm thinking it could make for a very inexpensive alternative to the 3Doodler printing pen for those with a steady hand, or anyone who sees melted snowmen and piles of unicorn poo as art.
Even less expensive: making sodium acetate yourself from baking soda and vinegar. What? No, I'm not going to tell you how. Google that shit yourself.