Research In Motion (NASDAQ:RIMM), maker of the popular BlackBerry smartphone, wants its slice of Apple's (NASDAQ:AAPL) iPhone pie.

On Monday, the smartphone maker announced in a blog post that it is preparing Mac OS-compatible software to allow its BlackBerry users to sync their devices with a Mac. The company expects to ship the Mac edition of BlackBerry Desktop Software to users in September.

If the comments to RIM's post are any indicator, there's a huge opportunity here. Users gushed over the possibilities that the new software represents.

"Thank God! I thought I was going to have to go to AT&T (NYSE:T) and the iPhone to properly sync up with my Mac, but now it looks like I will finally have it all," wrote one commenter.

Take note, investors: The iPhone may be burying Nokia (NYSE:NOK), Motorola (NYSE:MOT), and most other smartphone competitors here in the U.S., but there are still plenty of Mac-wielding CrackBerry addicts. They're not switching; they just want more love. They want better software.

Palm (NASDAQ:PALM) knows this, too. It's playing its own software card, but in a different way. CEO Jon Rubinstein talks up the Pre's webOS in a way that positions both the iPhone's lightweight version of the Mac OS and the BlackBerry OS as aging rivals.

"The most important indicator of our success is that customer response has been simply great, especially to Palm webOS," Rubinstein said recently. "Just as Palm pioneered PDAs in the 90s, we believe it has now pioneered the mobile operating platform for the next 10 years and beyond."

RIM's executives would likely disagree, as would Apple CEO Steve Jobs. What matters is that both Palm and RIM are trying hard to give users reasons to forego the iPhone. They've been less than successful thus far.

Now, Research In Motion is trying a Trojan Horse strategy -- a simple way to sync a Mac and a BlackBerry. Don't be surprised if it's rewarded with at least a sliver of Apple's pie.

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Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. He owned stock and options positions in Apple and a stock position in Nokia at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. The Fool's disclosure policy prefers to be stationary for its research time.