As silly as it sounds, this water warmer for baby bottles: https://a.co/d/hhJzLBn Nothing's worse than trying to mix the perfect water temperature at 3 AM while the baby is screaming, waking up the rest of the family. (We use pre-boiled water for the baby's bottles, so it's not as easy as adjusting a tap.) We bought this after we had our second baby and it's made feeding the baby slightly less stressful.
I use the hot water outlet on my espresso machine. It's temperature controlled by a PID