US company Altec Lansing has unveiled a portable speaker unit for Apple's iPod, which can turn the portable digital music player into a miniature bookshelf stereo.

The portable speaker set, InMotion, is priced at around £110. It comprises a cradle for the iPod and two speakers either side, each about the size of the player itself. It is designed for use with the full-size iPod, but Altec Lansing is offering buyers a free adaptor so it can also be used with the newer IPod Mini devices.

The unit is about the size of a paperback book when folded shut, it measures 23x137x30mm. It is easy to tote around, and weighs just less than a pound. If you're travelling, you can set it on a nightstand and use the IPod's Alarm Clock feature to turn it into a musical alarm clock.

InMotion's four speakers deliver surprisingly good sound. But while the InMotion's MaxxBass technology delivers excellent bass, Apple's bundled iPod headphones offer crisper, more-balanced audio overall. For example, when the InMotion blasts out rock tunes, a snare drum or tambourine occasionally sounds too loud.

The InMotion sports a built-in docking connector, so it works best with docking iPods. When connected to AC power and your Mac, it can serve as a complete dock replacement, automatically charging your IPod and syncing it with your Mac's iTunes library, ICal calendar and Address Book.

The InMotion can get power from the supplied AC adapter, a clunky-looking unit, or from four AA batteries. It also works with earlier iPods via its auxiliary input, but the recharging and synchronising features work only with docking iPods.