If you're in the market for energy efficient iPhone speakers, you won't find any that use less than the zero-electricity Koostik. Made from solid wood, the setup naturally amplifies the sound from your iPhone speaker, providing louder music without using any additional electricity. The Koostik site notes that the device works better for some types of music than others. So it may not be your cup of tea if you're into "Heavy Metal at high volume or heavy sub base sounds." The Koostik comes available in walnut, cherry or birdseye maple wood. No indication as to whether or not the woods are FSC-certified.