ABI Research, a market intelligence company specializing in emerging technology, has estimated that "aftermarket mobile phone accessories" will be a more than $50 billion industry by 2015.
"Smartphones are generally higher-value products than feature phones, so consumers are willing to spend more on the accessories for them," ABI senior analyst Michael Morgan says. "There is also a shift to higher-quality accessories, replacing the cheap, white-label products that characterized the market until recently."
Among the added accessories popular among consumers are protective and decorative cases, screen protectors, extra chargers, ear buds, noise-canceling headphones, stands, Bluetooth headsets, external speakers, belt clips and neck straps.
ABI estimates that the average smartphone owner has spent an additional $60 accessorizing their device.
The online shopping and review site Retrevo found that some smartphone owners spend much more.
It polled smartphone owners under the age of 35 and found that 9% of iPhone owners have spent $200 and up; 19% spent $100 to $200. Meanwhile, 6% of Android owners spent $200 and up, with 8% spending between $100 and $200.
Ninety percent of iPhone users described cases as a means of "self-expression," and 27% reporting that they had chosen a specific case to match an outfit.