Ember's temperature-controlled smart mugs have been going up in price over the last couple of years -- most likely due to supply chain issues -- but they now come in more color options, including some new eye-catching metallic colors that cost a little more than standard black, white or blue mugs.
Ember makes 6-ounce, 10-ounce, and 14-ounce size of its smart mug that keeps your hot beverage of choice hot while you sip it over a longer drinking session. While it won't keep your coffee or tea warm for hours, the idea is that you can select your ideal temp via the companion Ember app for iOS or Android and keep your beverage at a high temp during the 30 minutes or so it takes to casually drink it.
I personally prefer the larger 14-ounce version, though it does cost more. A good insulated mug with a top on it will also keep your beverage hot (and they are cheaper), but this Ember mug allows you to drink a cup of joe like you normally would and not sip it through a small hole in the top.