That’s the day the world changes. The day the mute will talk, the deaf will hear and the lame will walk. It will be Christmas in June, New Year’s in summer and Valentine’s Day all rolled into one.

It’s the day Apple’s iPhone hits the streets.

Yes, that thin wafer of delight, that electronic phenom delivering the Internet to the palm of your hand, that latest electronic gizmo that signifies you have arrived, finally lands on store shelves at the end of this month. Part iPod, part cell phone, part PDA, the iPhone is not your typical mobile communications device.

Featuring a touchscreen interface, the iPhone plays music, video, tracks appointments, stores photos, does e-mail and includes built-in Yahoo and Google search capabilities. It downloads music, connects with the Web and delivers crucial information, like stock and weather reports, in real time. Plus, it has that certain flair, that certain technological panache that only Apple can deliver.

But will it sell?

First of all, it’s going to set you back a few bills. An iPhone with four gigs of memory will run $500 and an eight-gig model goes for $600. Clearly this isn’t the kind of phone telcoms hand out for free in exchange for signing a multi-year plan.

And you have your choice of carriers, as long as it’s AT&T and you sign for at least two years of service. Right now the communications giant is the only iPhone carrier. What’s more, there are indications that the AT&T / iPhone combo is hardly your average cell phone / carrier arrangement.

Unlike other carriers that provide their own music download stores, the iPhone connects directly to Apple’s iTunes. In fact, you have to have an iTunes account for the phone to work. This ensures that Apple bills iPhone customers directly for their iTunes downloads instead of having to work through a mobile phone carrier.

Servicing will be different too, with iPhone customers bypassing AT&T to deal directly with Apple. AT&T’s job is to supply the wireless network. Apple will handle everything else.

But then, Apple isn’t so much presenting the iPhone as a new mobile as it is marketing the device as a new iPod. “The best iPod ever,” is how Apple CEO Steve Jobs describes it.

And, if you believe the rumors and speculation, the iPhone represents several new opportunities for Apple.

Like the opportunity to sell more Macs. Recently, Investor’s Business Daily reported that iPhone’s “halo effect” could lead to more Macintosh sales. It quoted a Morningstar representative as saying Apple’s future Mac sales could grow 20 percent per year for the next five years, a growth rate described as about twice that of the overall personal computer industry.

Then there are the rumors that Apple wants to get into the video rental biz. Sure, the company already sells some movies through iTunes, but there’s talk that the company plans to launch a video rental download service by fall.

Presumably, the rentals would time out and cease to play after a predetermined time has passed or after a certain number of views. However, rigid pricing and Apple’s refusal to tweak the iPod and iPhone to prevent pirated movies from playing on those devices has kept many major studios from participating in Steve Jobs’ vision of the future.

Perhaps the biggest sign yet that the iPhone is a big deal is that at least one company is already marketing an iPhone alternative.

Taiwan smartphone maker High Tech Computer Corp.(HTC) recently unveiled a new phone that tries to emulate the look and feel of Apple’s iPhone, including a similar touchscreen interface. And other companies are expected to follow in HTC’s footsteps if the iPhone takes off.

But despite all the marketing muscle Apple has poured into its new product, success or failure will depend on consumer acceptance of the iPhone. So far, interest has been heavy, with both Apple fans and casual iPod users showing iPhone envy. With prices starting at $500, and with only one carrier providing the connection, potential customers might choose to hold the line on an iPhone purchase come June 29th.