The issue is the amount of energy produced (minuscule) and the requirement for very humid air. It's also likely that the device needs to be colder than ambient temperature if I've got my thermodynamics right, so removing heat might be necessary, obliterating any gains and turning it into a dehumidifier that produces a small amount of waste electricity.

It might be another option in the pile of 'energy harvesting' solutions, where you need microwatts to miliwatts to power devices like remote temperature sensors, to avoid fitting ten-year lithium batteries. It doesn't seem likely to go beyond that.