Research In Motion (Nasdaq: RIMM) had better watch out. Apple (Nasdaq: AAPL) is invading its business-user turf in a big way.

With a software update early this summer, the iPhone will become more like an iBlackBerry. The hitherto consumer-oriented gadget will then be able to integrate with Microsoft (Nasdaq: MSFT) Exchange servers for quick access to email, tasks, and calendars, along with new security features that business users have been asking for, and an open application development toolkit.

The fact that Microsoft stepped in to provide some of the essential tools is surprising: This might be the first time the two Steves (Ballmer and Jobs) step onto the battlefield as brothers in arms rather than bitter enemies. And you might remember the brouhaha between Apple and Cisco Systems (Nasdaq: CSCO) over the iPhone brand name. Now, Cisco provides the VPN secure network functionality for the iPhone 2.0. Time and money heals all wounds.

Steve Jobs is putting his tasty apple pie right next to the blackberry cobbler at a time when RIM is moving in the other direction. The BlackBerry Pearl and Curve models are overt advances into consumer territory, and while they're nowhere near as mind-blowingly cool as the iPhone's endless touchscreen interface, they are compromises between what business needs and what entertainment wants. But you can't help but think that it's easier to teach the iPhone to do enterprise tricks than it is to give the BlackBerry a truly stylish makeover.

The distinction between the two leading smartphones thusly blurs a bit more, and nobody knows how phones based on the Google (Nasdaq: GOOG) Android platform will fit into that picture. Also, worldwide cell-phone leader Nokia (NYSE: NOK) has opened up its own mobile application platform. Add in Microsoft's Windows Mobile software, and we have a complete profusion of confusion.

Consider the opening gong struck. The battle royale over every kind of mobile device user is on. Whoever wins, the BlackBerry has never looked as firmly destined to sink in commoditization quicksand as it does today -- and that's saying something. Way to go, Steve and Steve.

Further Foolishness:

Microsoft is a Motley Fool Inside Value pick and Apple is a Motley Fool Stock Advisor recommendation.

Fool contributor Anders Bylund is a Google shareholder, but holds no other position in any of the companies discussed here. You can check out Anders' holdings if you like, and Foolish disclosure divides and conquers with practiced ease and elan.