Accessories aimed at the iPod nano 4G crowd are always a curious affair. Isn't the whole point to have your tunes on-the-go, with a minimal of fuss? And aren't costly (and bulky) add-ons the definition of "fuss?" We seriously doubted there was much of a market for the portable speaker attachment we saw a few weeks back, and now it's Radiopaq's turn to get us scratchin' our heads. The iPod Sound Jacket claims to do away with "the distortion that can sometimes result from a static EQ setting" and reveal the "hidden detail in the music that is lost during MP3 compression." In other words, it seems to be