Or just get a hot mist humidifier, which does this except:
1. Electronically (ex: you can do this in your bedroom directly, or anywhere you need the warm-mist)
2. With safety measures (its still dangerous, but they minimize the amount of boiling water to minimize the possible harm. Better than an entire pot of boiling water, but still half-a-cup of boiling water can severely burn you still)
3. Probably as cheap as the pot you were using to boil water anyway. Warm mist humidifiers are like $35.
Unless you have a gas stove, in which case prolonged boiling could lead to indoor air quality issues (unless you turn your fan on - but then you're drawing in cold air.
If you have an electric stove, boiling water will be less efficient than evaporating water and letting your heating system make up for the loss in sensible heat unless you have an electric furnace.
