You thought the iPhone was big before? Well, it's about to explode.

First of all, Apple sent out invitations today to a special event for March 6 to reveal an "iPhone software road map" which is likely to include the iPhone/iPod Touch SDK promised for the end of February. The SDK is expected to be joined with an Apple-planned pathway to distribution of third-party iPhone software via iTunes, and this will no doubt be accompanied by some early-program developers seeded by Apple to have apps ready to go at the SDK's announcement. 

Third-party apps is big enough news as it stands. Opening up the iPhone to outside developers means a steady stream of applications is virtually assured — both big apps that everyone will want and the equally important little apps aimed at specialty markets that will let everyone customize their iPhone to do the everyday jobs they need (or just dream about). iPhone is not just a phone — it is a new computing and communications platform. Third-party apps and a way to distribute them makes the platform infinitely more valuable to consumers.

But Apple decided to kick it up a notch for this event, adding that they will have some exciting new enterprise features to show as well. Other than an upgrade to 3G connectivity, this is the only announcement they could have made for this event that would actually be more exciting than the SDK itself. The one weakness of the iPhone up front was business connectivity. Only recently has AT&T even supported the iPhone on business phone contracts. If Apple can announce fuller connectivity with Microsoft's mail and calendar platforms and Lotus Notes, and other initiatives to make the iPhone a real alternative to the Blackberry for the serious business user, look for a second run on iPhones that might make the first one look thin by comparison.

What does this do for the Apple-centric family, meshing this platform with a growing dependence on Apple as their entertainment provider? Plenty. As I said, the iPhone platform is about more than phone calls. This platform (supported by the un-phone member of the clan, the equally-capable entertainment-oriented machine called the iPod Touch) is a quantum leap beyond the iPod as a personal entertainment device. And it's about to open up, big time.

Look at Apple's success as an entertainment provider. This week, we learned that Apple has become the number two provider of music in the United States. Moreover, they are expected to pass Wal*Mart to become Number One sometime yet this year. How have they accomplished this in such a short amount of time? According to analysts at NPD Group, Apple hooked teens on downloadable music purchasing (where everyone else from Wal*Mart themselves to Amazon has been much less successful) by making it easy for them to buy without the use of credit cards (via the iTunes Store gift cards available at practically every retail store in the country). Interestingly enough, some of the biggest growth for the iTunes Store this year came not from those heavy music buying teens but from people of middle years, 35-50. Why? Perhaps we oldsters can go to the iTunes Store and actually find the music we want without being embarrassed by the uncomprehending looks of 18-year-old store clerks. (As small as Wal*Mart's selection of CDs has become, it is no wonder people are turning to the iTunes Store in — excuse the pun — record numbers.)

Apple makes it easier and easier to spend money. With an iPhone or iPod Touch you can buy music directly from the portable device itself. Apple's deal with Starbucks lets you walk in there and use their wireless connectivity to buy from the iTunes Store's online version — free. Want to bet that you won't be able to do the same thing with iPhone software sometime soon after March 6? Third party apps on this most ubiquitous new mobile device will be turned to serve the home entertainment user, too. Games, software, media, even ebooks are likely to be available for this platform soon with the same instant-gratification system that is about to make Apple the Number One music purveyor in the nation.

Big? You haven't even begun to imagine how big the iPhone can be. March 6 kicks off the second wave. Prepare to be swept away.