Developers, who had been limited to using software simulators of the watch, discovered new possibilities.
Ross Cohen, chief operating officer of BeenVerified.com, which makes a caller ID app for the watch, said he only realized on Friday that the watch goes on and off automatically as you raise or lower your wrist.
The simulator did not have a microphone, leaving some developers to guess how well it could hear. Having the watch on hand will speed development, said Danielle Keita-Taguchi, marketing analyst at Y Media Labs, which has designed apps for companies like American Express, EMC and eBay.
"A lot of Fortune 500 companies really want to leverage this new technology quickly," she said. "Health, transportation and social media will be the three main industries that will utilise the Apple Watch."
(Also see: Apple Reportedly Aims to Ship More Than 20 Million Smartwatches in 2015)
Tracking firm App Annie counted 3,061 total apps supporting Apple Watch on Friday. Some 10 percent were games. Productivity apps were 8 percent and lifestyle and health/fitness each accounted for 7 percent.
Ride-hailing service Uber had an app, as did sports network ESPN, microblogging platform Twitter, photo sharing service Instagram, tune-identifier Shazam and the Outlook email app from Microsoft Corp.
Notable absences included social network Facebook, message service Snapchat and any apps from Google Inc. A Google spokesperson said "only time will tell" if it would make any apps for Apple device. Snapchat could not be reached for comment. Earlier this week Facebook CEO Mark Zuckerberg told analysts who asked about the watch, "We're going to watch closely and build what our community wants us to."
So far developers see the watch's main benefits as saving time or the labour of frequently taking out a phone.
"I've got my phone with me already, why do I also need the watch?" asked Matt McIlwain, managing director of Madrona Venture Group, which backs a host of software companies. "What is the extension benefit to having it on my wrist versus in my pocket?"
McIlwain's firm has invested in Redfin, the online real estate service, which has one answer. Its Apple Watch app that let users find nearby homes for sale and dictate notes on homes visited.
© Thomson Reuters 2015
For the latest tech news and reviews, follow Gadgets 360 on X, Facebook, WhatsApp, Threads and Google News. For the latest videos on gadgets and tech, subscribe to our YouTube channel. If you want to know everything about top influencers, follow our in-house Who'sThat360 on Instagram and YouTube.