Drifting OT.. I have a use for this low-grade waste heat. I park my car on the driveway just a few feet from the boiler vent so in winter it's very frustrating scraping off windscreen ice, getting into a cold car and starting with a rich fuel mix, right next to all those nice warm fumes.
What I'd like is a quick fit/release heat-pipe with one end in the boiler vent and the other in the sump or radiator. I don't know if you'd need a circulating pump too like the Kenlowe device has. I've worked with small heat pipes in computer cooling systems and they are incredibly efficient (a good trick is to get someone to stir their tea with one). Would the idea scale up to a few metres?