Stainless steel cubes or “pucs” as the vendor calls them, intend to chill your drink, without having to go through the trouble of using ice cubes and having the drinks watered down, or have a change in the flavor thanks to the added water. The gradual conducting cubes soak up in the temperature to add to the cooling.
By the same logic, they could as well be applied to hot drinks like coffee and tea to keep them warmer for a longer duration. Because these stainless steel pucs, they don’t discriminate. Available in sets of six, they’re currently running for pre-orders/funding on Kickstarter.