Longer-lasting batteries are crucial for a new crop of wearable computers whose rise may upend Apple and Google's dominance of mobile devices, two of the field's pioneers say.
Wearable devices - from bracelets that monitor physical activity and sleeping patterns to clothing with built-in sensors and Web-ready glasses - may mark the next big technology shift, just as smartphones evolved from personal computers.
That transition has put the unglamorous battery in a starring role.
"All this wearable stuff is constrained by battery technology. It's not a computing problem," Hosain Rahman, CEO of Jawbone, told the Reuters Global Technology Summit on Monday.
While battery technology has not expanded at the same clip as miniaturization and displays for instance, some wearables pioneers are hopeful for a breakthrough in coming years.
"There are other things that will come up five years down the road like remote charging that will cause a huge next leap because it breaks this dependence on the battery. But right now the biggest challenge is the battery that's small enough and serves you," Soulaiman Itani, chief executive of Atheer Labs, said at the summit in San Francisco.
Itani likened wearable computing's current stage of evolution to smartphones during the mid-2000s.
"It's at the Palm stage, and you need an iPhone to come out," Itani said, referring to Palm Pilots that predated the 2007 iPhone that won strong reviews but was rendered defunct after Apple's seminal device was launched.
Rewriting the rules
According to Forrester Research, about 5 percent of online U.S. adults say they wear a device with a sensor that can monitor some form of activity, such as running or sleeping.
Asked what gadget they would be most keen on using, 29 percent of participants cited a device that clips on to clothing.
Devices that attach to the wrist were close behind with interest from 28 percent, while glasses trailed other options, garnering interest from 12 percent of the participants.
Google is testing a $1,500 version of Glass, a stamp-sized electronic screen mounted on a pair of eyeglass frames. Apple and Samsung Electronics are said to be working on other forms of wearable technology, such as a smartwatch.
Apple Chief Executive Tim Cook has called wearable computers an area "ripe for exploration." But during his comments at the AllThingsDigital conference last month, he stopped short of confirming reports the company was developing a smartwatch.
Google and Apple, which have the two most popular smartphone operating systems, have the heft to boost the nascent market and potentially control it, thanks to a vast number of users and the hundreds of thousands of apps that run on their software.
Some think the market for wearable computers won't take off until Apple enters the fray, providing the kind of clever design and marketing blitz that helped transform smartphones into a must-have consumer item.
"If Apple enters the market that would be a rapid leap forward," said Forrester analyst Sarah Rotman Epps. "Apple is a market maker. Any Apple device can sell tens of millions of units."