BESTINNKITS Gravity-Sensing Mug Warmer

There’s no on or off button on this mug warmer. Set a mug on it and a gravity switch starts the heat; lift the mug away and it stops. A small light shows when it’s working, and that’s the entire interface.

Under the mug is a 19-watt plate with a heat-conducting glass top that wipes clean after a splash. It keeps coffee, tea, milk or cocoa warm at up to 131 degrees Fahrenheit, so a drink can last through a long stretch of email instead of going cold after three sips. It’s compact enough for a desk or a nightstand, and it can double as a warmer for candle wax.

It suits the person who pours a cup, gets pulled into a call and finds it stone cold an hour later, every single day. It’s a cheap, simple alternative to a heated smart mug, because it works with a mug they already own and love.

The catch: it keeps coffee warm rather than piping hot, and it’s picky about the mug. Thin-walled, flat-bottomed mugs work best, while raised, concave or heavily insulated bases warm less well. The switch also needs at least 0.8 pounds pressing down, so a mug that’s almost empty may not keep it running.