It has been four years since Apple Inc (AAPL.O) introduced a completely new gadget and the pressure is on for the world's largest tech company to wow at its "special event" in Cupertino, California, on Tuesday.

Apple has fed the high expectations, with promises by executives that the company's best product pipeline in 25 years is being readied inside its secretive facilities. That's a high bar for a company whose hits include the modern, graphic-based personal computer, the smartphone, the iPod and the tablet PC.

Those now ubiquitous gadgets were created under the innovative and famously meticulous eye of Apple co-founder Steve Jobs, who died in 2011. When Chief Executive Officer Tim Cook takes the stage on Tuesday, technology aficionados, investors and rivals will be watching closely to see whether Jobs' handpicked successor inherited the magic touch or whether Apple's winning streak is coming to an end.

"We think Apple’s pipeline is finally going to satisfy those who have wondered if the company has any new products. The stock price has been rallying as investors are beginning to believe that Tim Cook all along was telling the truth that there is an incredible pipeline of products," said Michael Yoshikami, CEO of Destination Wealth Management.

In the last five years, the period beginning July 1 has been the most fruitful for holders of Apple shares, with an average price gain of about 22.5 percent, compared with 11 percent gains seen in the first half of the last five years.

Below are some of the key products and features to look out for at Apple's big event on Tuesday:

iWatch?: Rumors of an Apple smartwatch go back several years, but Tuesday may finally be showtime. The watch, which will reportedly have a flexible screen and come in two sizes, will track its wearer's health and fitness, double as an electronic wallet and of course, display messages.

The watch is not likely to go on sale until sometime in 2015 and Apple may not even reveal its price on Tuesday. But with rivals such as Google Inc (GOOGL.O) and Samsung Electronics Co (005930.KS) already entering the smartwatch market, tech-watchers are anxious for Apple to show its cards.

"The market has been waiting for Apple’s product as the real category-defining product," said FBN Securities analyst Shebly Seyfari.

iPhone 6: Smartphones are Apple's bread-and-butter, representing more than half of its revenue, and the company is expected to introduce a pair of new models with bigger screens, a sleeker design and wireless payment capabilities. The iPhone 6 will be available with 5.5-inch or 4.7-inch screens, a step up from the current models' 4-inch screens. There is also speculation that some phones will boast extra-tough screens made from scratch-resistant sapphire material.

Mobile Wallet: Apple has reportedly struck deals with major credit card providers Visa Inc (V.N), MasterCard Inc (MA.N) and American Express Co (AXP.N). The partnerships, as well as a special communication chip within the new iPhone and smartwatch, would allow consumers to use their gadgets at stores to buy everything from coffee to blue jeans - changing the shopping experience and extending Apple's reach from the Web to real-world commerce.

Health: Apple's launch of the "HealthKit" data service earlier this year made it clear that it sees its products helping consumers manage personal health information. By incorporating the HealthKit service into the iPhone 6, and by packing its smartwatch with sensors capable of monitoring physical movements and heart rates, Apple could lay the groundwork for a broader push into mobile healthcare.

One More Thing? Apple's Jobs was famous for surprising fans with unexpected products at the end of his presentations. Could Cook preserve the tradition with a peek at a long-awaited Apple television, a rumored bigger iPad or a completely unexpected product?