Smartphones command a great deal of the excitement and attention in the wireless market, but the less-flashy accessories market also is booming. After-market mobile phone accessories--those sold to users after they purchase their phone--produced worldwide revenue of $26.5 billion last year, according to ABI Research. And that volume is expected to increase to slightly more than $50 billion in 2015. The reason? Growing sales of smartphones drive up accessory sales as customers seek to get the most out of their new devices. What's hot and what's not? FierceWireless, using ABI survey data, produced a list of the top five categories of after-market accessories in 2009. Special feature