The Caframo Ecofan 800 was the first model released in the ecofan series. It has some limitations when compared to it's big brother, the Ecofan 802, but is still a servicable and worthwhile addition to your woodstove. All of these fans use the "Seebeck Effect" to generate the electricity that powers the fan directly from the hot metal surface of your stove. No need for batteries or a mains connection
While I have yet to use one of these specific fans myself reviews and comments from users seem positive. The trouble with assessing these fan's effectiveness is that the results are relatively intangible. Most users report that the fan helps distribute warmth throughout their rooms making the space "feel" warmer but it is hard to quantitatively test this. Overall impressions are very positive however, and the principal is sound.
Some users have experienced technical issues, especially related to the ecofan 800 overheating. If the parts overheat components may be permenantly damaged, voiding the warranty. There is a safety feature built in to prevent this (a bimetalic strip the lifts the front edge of the ecofan if the stove surface gets too hot) but by all accounts it is still possible to overheat the fan. This is largely resolved in the larger 802 version.
The 800 is a less effective model than the larger, and more powerful, Ecofan 802 but may be a viable choice for a smaller space.
While the 800 has been recently discontinued (Autumn 2012) some stockists are still carrying these - do make sure you check prices though as the newer models may still come in at competitive prices.