Apple unveils two new iPhones -- the 5S and 5C

The iPhone 5C was the first phone demoed at Tuesday's event at Apple's Cupertino, California, headquarters.

"It has an incredible all new design, one that's more fun, more colorful than any iPhone we've made yet," said Phil Schiller, Apple's senior vice president for marketing. In a video, Apple design guru Jonny Ive described the 5C as "beautifully, unapologetically plastic."

The phone will sell for as little as $99, for a 16GB version, and $199 for one with 32GB of storage (each with a two-year mobile contract). In a departure, Apple will also be making its own cases for the 5C, selling them in a variety of colors for $29.

Then there's the iPhone 5S, which is the more traditional update to the iPhone 5.

"It is the gold standard in smartphones," Schiller said.

The 5S features a handful of performance upgrades, including what Apple calls a dramatic increase in processing speed.

It will have the first 64-bit chip in a smartphone -- Apple's A7 -- which Schiller said has tested at up to twice as fast as the iPhone 5's processor. It also will have a new feature, a motion co-processor, that will let the phone be used as a fitness tracker along the lines of a FitBit.

Schiller said battery life will be "the same or better" than the iPhone 5 and its camera will have 15% more active sensor space, improved white balance and auto-focus, and a new flash.

Also, its camera will, for the first time on iPhone, allow video in slow motion.

Arguably the most dramatic new feature on the phone, though, is Touch ID, a fingerprint scanner for added security. Users will be able to log into their phone via the home button and make purchases from iTunes using their fingerprint as a password of sorts.

The iPhone 5S will sell for $199 for a 16GB version, $299 for a 32GB model and $399 for the top-end 64GB phone.

Pre-orders for the iPhone 5C starts on September 13. Both versions are on sale starting September 20. Cook also announced the newest version of Apple's mobile operating system, iOS 7, will be released to the public on September 18.

It will have over 200 new features, according to Apple, including the ability to switch voice-activated digital assistant Siri to a male voice.

The iPhone has remained the world's top-selling smartphone, save for a few quarters when it was dethroned by phones in Samsung's Galaxy S line. But after making up nearly 24% of all smartphones sold in late 2011, Apple's device is now down to about 14%, while Android phones account for a whopping 79%.

With the iPhone 5C, Apple is clearly looking to emerging markets like China and India, where a less expensive phone would, presumably, sell well to a massive potential customer base.

Historically, rollouts of new Apple products have been near-mystical affairs for fans. But as the smartphone market has matured, some analysts say the real excitement may need to come from other products.

"Apple needs a new 'hero product,' but I do not think it necessarily has to be a phone," Gartner technology analyst Carolina Milanesi told CNN. "With technology innovation slowing down, maybe they are better off turning iPhone into a market-share grabber and showing innovation in another product."

A likely candidate could be the company's anticipated "iWatch." Apple is all but certain to join the emerging smartwatch market that Samsung entered last week with its Galaxy Gear device.

Also, Apple has also long been rumored to be working on a TV set.