Most cellphone charms do nothing but sit there and be charming, but this one by Lava Lamp creator Mathmos actually serves a useful purpose: It blinks red (or blue, your choice) when you have a phone call coming in. Might be a good compromise between setting that phone on vibrate and possibly still irritating those around you, or missing all your calls. If you don't care for this retro-chic lava lamp replica, you can also get one shaped like a miniature light bulb.
While we're not keen on having any kind of charm clanking around in our pockets along with a cellphone—likely scratching it up severely—this is one of the most useful cellphone charms yet. It's not even actually plugged into the cellphone, either, working by picking up the RF interference from the phone as receives a call. Not sure if that works every time, but it sounds like a good idea, one that might be worth the $12 plus shipping it would take to find out. [Technabob]