SAN FRANCISCO — – Siri may be feeling a little job insecurity.The sometimes-droll assistant on Apple's iPhone and iPad that answers questions and helps people manage their lives is facing competition from an up-and-coming rival by Google. The duel began Monday with the release of a free iPhone and iPad app that features Google Now, which performs many of the same functions as Siri.It's the first time that Google Now has been available on smartphones and tablet computers that don’t run the latest version of Google's Android software. The technology, which debuted nine months ago, is being included in an upgrade to Google's search application for iOS, the Apple Inc. software that powers the iPhone, iPad and iPod Touch. It's up to each user to decide whether to activate Google Now within the redesigned Google Search app, which is available through Apple's app store.Siri tried to dismiss the competitive threat. When asked for an opinion about Google Now, Siri responded: “If it's all the same to you, I'd rather Google later.”Mike Allton of St. Charles, Mo., who has owned an iPhone for four years, could hardly wait to check out Google Now, even if Siri might interpret it as a betrayal.Siri “is looking a little green with envy,” Allton, 36, said with a laugh after he installed Google's new app. “I love Apple products, but I like to see the competition because it probably will lead to even more improvements. I believe this technology is going to be even more deeply ingrained in our lives a few years from now.”Other iPhone users, even those who have grown fond of Siri, welcomed Google Now's arrival to iOS in mostly enthusiastic and sometimes amusing remarks posted on Twitter and Google Plus. One person joked that Google Now is so helpful that it prompted him to wash his hands after using the bathroom. The biggest gripe was about the possibility of Google Now's location-tracking features draining a device's battery more quickly.Google Now is Google Inc.’s latest attempt to lure iPhone and iPad users away from a service that Apple built into its devices.Google quickly won over millions of iPhone users in December when it released a mapping application to replace the navigation system that Apple dumped when it redesigned iOS last fall. Apple's maps app was inferior to Google's ousted service. The app's bugs and glitches made Apple the butt of jokes and fueled demand for Google to develop a new option.Apple has been losing to Google on other fronts in a rapidly growing mobile computing market, an arena that was revolutionized with the iPhone's release in 2007. Smartphones and tablet computers running Google's free Android software have been steadily expanding their market share in recent years, partly because they tend to be less expensive than the iPhone and the iPad. At the end of 2012, Android devices held about 69 percent of the smartphone market while iOS held about 19 percent, according to the research firm IDC.Android's success has been particularly galling for Apple because its late CEO, Steve Jobs. believed that Google stole many ideas for the software from the iPhone. That led to a series of court battles over alleged patent infringement, including a high-profile trial last year that culminated in Apple winning hundreds of millions in damages from Samsung Electronics, the top seller of Android phones. That dispute is still embroiled in appeals.The rise of Android is also squeezing Apple's profit and has contributed to a nearly 40 percent drop in the company's stock price since it peaked at $705.07 in September around the time the iPhone 5 came out.Android's popularity is good news for Google because the company's services are built into most versions of the operating system. That brings more traffic to Google services, creating more opportunities for the company to sell ads – the main source of Google's revenue.Apple bills Siri as an “intelligent feature.” Since its release in October 2011, Apple has made it a centerpiece of some marketing campaigns that depict Siri and its automated female voice as an endearing and occasionally even pithy companion.