This portable iPod speaker dock from Voix allows you to click your iPod in to place surrounded by a secure cocoon of speakers.
Powered by mains or batteries, it's compact, lightweight and compatible with the iPhone, Touch, Classic and nano (there's a line input for other portables). And you can turn it horizontal for movies.
There's little in the way of bass, and a harshness to the treble at loud volume. But hey, if you really want something compact, portable and battery-powered that adapts for videos, then this does a job