Apple is launching the iPhone 4S this week with the recently unveiled integration of Siri, a voice activated "assistant." Siri accepts voice input and can perform a range of actions on your iPhone, including looking up information, adding calendar events, and even composing short texts and e-mails.

Siri shows a lot of promise in realizing human computer interaction using natural language. Right now, however, Apple seems to be wisely keeping the feature firmly in the "beta" stage even as it seeks to popularize talking to your cell phone to get things done. As iPhone 4S users start using Siri en masse, it's worth considering where Apple might integrate the technology in the future. Will talking to computers and devices transcend conventional keyboard or touch input, à la Star Trek?

Right now Siri is limited to the iPhone 4S. Presumably much of the reason for that limitation is that Siri requires a lot of computing power to work. Siri co-founder Norman Winarsky told 9to5 Mac that the Siri app, originally released in early 2010, required a number of workarounds and optimizations to work well on the then-current iPhone 3GS's 600MHz processor. Even with the significant processing boost gained from the iPhone 4S's dual-core A5 processor, however, Apple is still calling the tech a "beta" nearly two years after its first public release.

Apple has set pretty high expectations for Siri, and it likely didn't want to hamper it with compromises to get it to work on older hardware. After all, the company never quite lived down the mocking it received for early iterations of the handwriting recognition in its Newton MessagePad. Though later versions worked quite well (and the technology was eventually integrated into Mac OS X as Inkwell), its reputation for completely misinterpreting handwritten words never died.

However, the iPad 2 already has the relatively high powered A5 processor built in, so it's easy to assume it would be the next iOS device to get a Siri upgrade. Recent evidence buried in iOS 5 suggests Apple is already working on an A5-powered Apple TV, perhaps bringing support for 1080p video to the tiny set-top box. With an A5 processor, you could potentially tell your Apple TV to play the next episode of The Venture Bros instead of fumbling with its simplistic remote. Unfortunately, the iPod touch was passed over for an A5 upgrade for this holiday season, so it may be as much as a year before the iPod touch could potentially take advantage of Siri.

While these sound like easy things to pull off, the fact is that that these devices may not get Siri at all—at least not in the short term. Besides a relatively beefy processor to power Siri's natural language interpreter, it also relies on speech-to-text recognition technology from Nuance. This works by encoding and sending an audio file to Nuance's servers, which return the interpreted text to the iPhone. Without a constant data connection, Siri doesn't work, period. iPhones are rarely without data connections, but the same can't be said for WiFi-only iPads and iPod touches. Apple will still need to find a way to work the feature into these devices in a way that doesn't frustrate users when it isn't available after leaving the range of a convenient WiFi signal.

Another limitation may also be a device's included microphone. The iPhone 4S has, like its iPhone 4 predecessor, a secondary microphone used to filter background noise. Those with experience using Nuance's Dragon speech-to-text products for Windows or Mac OS X are undoubtedly familiar with the need for a good quality headset to get the best results—and even then accuracy isn't 100 percent. Given this, we believe that the relatively low quality microphones in the iPad and iPod touch again may not give the best results, and could possibly prevent these devices from using Siri in the near future.

The Apple TV benefits from having a constant network connection for speech recognition, but Apple would have to build in a microphone that can filter background noise well enough from approximately 10 feet. Alternately, the mic could be built into the remote (a suggestion we had for a speech-powered Google TV). Or, an iPhone could serve as a voice-activated remote for an Apple TV: "Siri, play season two of Mad Men on Apple TV."

More exciting, however, may be the prospect of integrating Siri into Mac OS X. All current Mac hardware is already capable of doing the necessary speech-to-text processing locally, so it doesn't need to be network-connected for Siri to work. (Siri was originally designed to be modular, according to Winarsky, so any voice recognition system could be plugged into it.) Mac OS X already has a fairly rudimentary voice control system built in, but Siri's artificial intelligence could take that to the next level. Imagine firing off tweets as fast as you could say them, dictating e-mails, searching for airline tickets, and more simply by telling your Mac want you want and letting Siri do all the work.

Big predictions meet big skepticism

Big predictions about the importance of Siri are already coming. Cross Research analyst Shannon Cross believes Siri is a pivotal technology. "We believe," Cross wrote in a recent note to clients, "the use of natural language and potentially the ability to distinguish between voices could one day change the way we interact with electronic devices and provide a substantial technology advantage to Apple. Quite simply, we have not seen a demonstration of comparable AI in any other consumer system."

Winarsky is perhaps even more bullish. "Apple will enable millions upon millions of people to interact with machines with natural language," he told 9to5 Mac. "[Siri] will get things done and this is only the tip of the iceberg. We're talking another technology revolution—a new computing paradigm shift."

However, the promise of the technology should be tempered with the realties of human interaction. Ars spoke to some of the creative minds behind Star Trek about the future of human computer interaction last year. While visual effects artist Doug Drexler believed voice interaction held promise, visual artist supervisors Michael and Denise Okuda were skeptical that it would be as useful as some may hope.

For instance, imagine talking to your cell phone, computer, or other device in a public space. With even a handful of people talking to their devices, the cacophony could quickly become a problem. "I don't want to hear people's phone conversations, let alone them talking to their devices," Denise Okuda told Ars.

Michael Okuda also noted that voice input is generally inefficient. "Imagine I'm looking at some photos, and I want to say, 'Up, up, left, down one, photo number 3362, no, the one on the left.'—that's much slower than just clicking or tapping," he said. "Natural language is, I think, going to have some significant limitations."

Still, in the confines of our own homes and offices, Siri's voice-based control could shave off a good amount of time performing mundane tasks like setting reminders or performing searches. And, such control could make computers and other mobile devices far more powerful for those who simply can't use keyboards or touch input due to injury or handicap.