No gadget is an island.

Without the right accessories, your portable electronics are only half as powerful as they have the potential to be. From more-compact speaker systems to higher-end headphones, battery boosters to other add-ons, a world of accessories is out there, primed and ready to help you get the most out of your favorite gadgets.

Speakers
Tons of iPod-specific speakers are currently on the market, but one of the best and most powerful is Altec Lansing’s tube-shaped inMotion iM7 ($249.95, alteclansing.com ). Insert any dockable iPod in the iM7, and the system will fill the room with music — all while charging your ’Pod. The iM7 comes with a built-in subwoofer for added bass, and a remote that lets you control your iPod from across the room. If you want to hit the beach or park, round up eight D batteries and you’re ready to roll. Not prepared to spend $250? Altec’s got a slew of more-than-respectable, lower-priced iPod speakers as well.

Battery Boosting
The iPod’s battery life is adequate most of the time — unless you need to fly from Boston to Bangkok, or you try to watch Lord of the Rings straight through without recharging. The Nyko iBoost battery pack ($69.99, nyko.com ) includes a lithium-ion battery of its own, so you can extend your iPod’s play time by an additional seven hours (for video) and 16 hours (for music). The iBoost attaches to the back of your player and clips into the dock connector, but it’s thin and light enough (just 2.5 ounces) that it won’t make you feel as if you’re carrying around a whole ’nother device.

Gaming Speakers
If you’re looking for an affordable portable speaker system with solid sound, you can’t do much better than JBL’s On Tour or On Tour Plus ($99.95 or $129. 95, jbl.com ). The On Tours plug into any mp3 player or gaming device’s headphone jack and feature a cover that you slide open when you want to listen to tunes. When you hit the road, you’ll need four AAA batteries, which provide about 24 hours of continuous play. The regular On Tour is white, while the On Tour Plus comes in black and is geared toward Sony PSP owners: it includes a carrying case and a bracket that attaches to the top and holds up the PSP.

Just in Case
If you’ve ever left an iPod floating loose in your backpack, you know how easily it scratches. A good case is a must, although picking the right one is really a matter of personal taste. If you like tight-fitting silicone-rubber cases, try iSkin’s eVo3 for the video iPod ($34.99, iskin.com ). It comes in six colors and provides full-body protection, including a clear-plastic screen guard. If you prefer to preserve the aesthetic of the iPod, check out Agent 18’s Shield cases ($19.95 to $24.95, agent18.com ), which encase your iPod Video, Nano, or Mini in a completely clear plastic shell while still letting you access the controls. For a more-traditional enclosure, consider Pacific Design’s Flip Case (either the Mini or full-size iPod versions, $19.99 to $29.99, pacificdesign.com ). These faux-leather cases flip open to reveal your iPod, and they come in a bunch of colors, each featuring a racing stripe.

Radio, Radio
Two of the hottest gadgets around are Apple’s iPod and Sony’s PSP. Yet neither comes with a radio that you can listen to when you want to catch up on news or you simply get bored with your music. Realizing its own deficiency, Apple has come out with the iPod Radio Remote ($49, apple.com ). It hooks up to your iPod’s dock connector and combines a remote control, FM tuner (which you control from the iPod’s screen), and earbuds (which contain the antenna). Likewise, Griffin’s iFM PSP ($49.99, griffintechnology.com ) combines an FM tuner and remote control in a tiny dongle that also includes a pass-through port for headphones.

Earphones
Most mp3 and portable media players come with cheap, cruddy-sounding earphones. If you care about the way your music and movies sound, you’ll want to upgrade to a pair that actually enhances the audio. Ultimate Ears’ super.fi 3 Studio sound-isolating earphones ($99.99, ultimateears.com ) slide straight into your ear canal and block out environmental noise, such as cars, conversation, and the sound of the crying baby one row behind you. The ’phones come with six pairs of tips in three different sizes, so even if you have Dumbo-size ears, you should be able to make them work. Like the Ultimate Ears’ ’phones, Shure’s i2c sound-isolating earphones ($129, shure.com ) insert straight into your ear canal to seal out ambient noise. However, the i2c features dual connectors: one for your mp3 player, one for your cell phone (provided your mobile has a 2.5mm headphone jack). A control switch lets you toggle between music and phone calls, and a mike allows you to keep up your end of the conversation. The only bummer: you won’t hear calls ring through on the earphones, so you’ll want to keep your phone on vibrate.