Why you must have it: The iPod is quickly becoming the modern stereo, but its digitized files often lack the nuance of the original recordings. SRS Labs' iWow for iPod Adapter plugs into the iPod's bottom 30-pin connector and restores the audio cues in the sources, so music and video files sound more like they were intended. (SRS Labs also offers the separate iWow Premium software, which is an iTunes plug-in for your Mac or PC that adds the same audio restoration to music and videos played from your computer.)
Your chances of having the first one on the block: High, as the new iWow hardware was released just this month. (The iWow Premium software shipped in October.)
What you must know: The hardware adapter is not certified for the iPhone, though users report it works when the iPhone is in airplane mode. SRS Labs released a Mac-only iWow 1.0 iTunes plug-in in 2007 for $30, and it quickly gained popularity. The latest iWow plug-in adds the enhanced versions of its capabilities to both Mac and Windows versions of iTunes and to your iPod directly.
What you need: Any iPod for the iWow hardware, and a Mac or PC with iTunes 6 or later for the plug-in software. The adapter costs $100, while the plug-in software costs $70.