A candle oven based on the most efficient wood fired home heaters - the kajelofen. After 45 minutes with a couple of tea lights in the bottom, this gets too hot to touch in the upper compartment, and the whole piece radiates heat for hours afterward. Some day I will get doors put on.
This Pin actually shows you how to build the candle and the supplies you will need to get it done. Will be deleting the other pin from the guy who wants you to buy it and tack on a ton for shipping. =/
the tealight and flower pot space heater functions as a small-scale masonry fireplace, reducing the convective losses and increasing radiation to the room, as opposed to an open candle which functions like an open fireplace, with most of the heat lost by convection up the chimney.