Monday is a big day for techies and the droves of investors who closely follow Apple (AAPL -0.35%) stock. The company will be making some "exciting announcements" during the opening event of its annual Worldwide Developers Conference, according to Apple. The tech giant must truly be enthusiastic about the announcements because it apparently wants the world to watch. The keynote, starting at 1 p.m. Eastern time, will be streamed live on the Internet.

Source: Apple.

What can we expect from Apple on Monday? As usual, likely an introduction of the newest versions of OS X and iOS. And on a more exciting note, hopefully a few surprises. Here are the key rumors that investors will be paying attention to.

Some Beats surprises?
With the acquisition of Beats Electronics announced just before WWDC, the timing suggests that Dr. Dre and Co. could potentially have some surprises to announce. The New York Post's Claire Atkinson, the first to report the finalized price of the Apple-Beats deal, says her sources believe Beats founders Jimmy Iovine and Dre will both attend the event.

Smart home platform
News about a potential Apple-based smart home platform first broke from the Financial Times earlier this week. The platform, writer Tim Bradshaw said, is "a new software platform that would turn the iPhone into a remote control for lights, security systems and other household appliances, as part of a move into the 'Internet of things'."

But now Gigaom is toning down the smart home platform speculation to nothing more than a smart home program that will simply certify devices as the "Made for iPhone" program does.

Who will be right? Or is the truth somewhere in the middle?

"Healthbook"
Potentially the biggest possible announcement -- one that could provide insight into Apple's product plans -- could be the introduction of a rumored app that aggregates various fitness and health information in a central location. The rumor mill is referring to the app as Healthbook. 

An introduction of a Healthbook-like app could give investors insights into Apple's plans for the iWatch, a smartwatch with biometric sensors that investors expect to be one of the products in a new category that Apple CEO Tim Cook has mentioned it is preparing to launch.

Even better, perhaps Apple will give a glimpse of its iWatch in order to display the functions of Healthbook. This, however, is unlikely. Re/code's sources "familiar with Apple's plans" say the company doesn't have plans to introduce the iWatch during the event.

Still a mystery
All in all, little is known about potential surprises Apple may unveil during the event. But since Apple's software plans aren't leaked as easily as its product plans, given the sprawling global supply chain required for it to mass produce its hardware, it's quite possible for Apple to make some completely unexpected announcements.

For Apple shareholders, surprises are nice -- but not required. The most important thing it needs to do for long-term shareholders next week is simply to clearly demonstrate that it can still further strengthen its ecosystem of software and services. Look for cutting-edge improvements to iOS and OS X that make Apple's operating systems more compelling to the marketplace than ever before.

Plan to tune into the live event? Bookmark this link and check in Monday at 1 p.m. ET.