Market research firm Gartner recently released a report projecting the used smartphone market to roughly double to 120 million units, or a wholesale value of $14 billion by 2017, CNET reported.

"With consumers in mature markets upgrading their smartphones every 18 to 20 months, the inevitable question is what happens to the old device?" Gartner analyst Meike Escherich was quoted as saying by CNET.

Previously, used cellphones primarily ended up in the hands of consumers in developing markets. But that's changing.

With consumers increasingly looking to tighten their purse strings, a year-old smartphone looks like a cool deal. And for those who hanker for the latest, selling off the old high-end phone is an attractive way to bolster their funds.

Many companies are capitalising on this trend. One such player is Gazelle, an e-commerce company that specialises in enabling people to sell used electronics.

In October, Gazelle began offering the option to also buy used smartphones.

"It's a huge market that's growing fast," Gazelle CEO Chris Sullivan said in an interview.

Gazelle's own studies found that within the same household, one member of a family could be constantly upgrading to the newest smartphone, with other members either taking the second hand phone or buying a cheaper used model.