The Apple iPhone (above) debuted Tuesday, January 9, at Macworld. Credit: Apple

Steve Jobs was exaggerating when he said that Apple's iPhone would be as groundbreaking a product as the original Macintosh and the iPod. The iPhone is not the first cell phone to run a Unix operating system: many cell phones today run a stripped-down version of the Linux operating system. And cell phones with touch screens that you can finger are common as well: instead of taking out the stylus, I usually run my Treo 750p with my thumb and index finger. Nevertheless, the iPhone does have a number of important innovations that are easy to miss in all the hype.

The first important iPhone innovation is the sensors that make it aware of its environment. According to Jobs, the iPhone has a proximity sensor that disables the screen and touch pad when you place the phone next to your head, saving both power and preventing your ear from accidentally hanging up on someone. Another sensor figures out which way is down, allowing the screen to automatically switch from portrait to landscape mode when you turn it on its side. The third sensor detects the amount of ambient light and lowers the intensity of the backlight accordingly. That's a great idea, although I had a clock that had such a sensor back in the 1970s. Perhaps Steve had the same clock.

The second innovation is the iPhone's new interface, which is based on gestures rather than on mouse clicks. The danger with a gesture-based interface is that the gestures that work aren't immediately obvious. Apparently, you can zoom into the iPhone's windows by pressing the touch screen with two fingers and then spreading them apart. My guess is that most of the phone's users won't figure this out. As the adjacent photo shows, the phone also has a theme of light buttons on a dark background; we'll see people find that more usable than the interfaces that dominate on phones today.

Mostly, though, the phone reflects good, solid engineering--what we've come to expect from Apple and what seems sadly lacking from most other players in the market. The phone is 11.6 millimeters thin, yet it has a touch screen, an ultra-high-resolution display, a two-megapixel camera, and five hours of battery life for talking and video, sixteen hours for music. Apple hasn't released the specs, but the phone clearly has a fast microprocessor. At $499 for the four-gigabyte version and $599 for the eight-gigabyte version (plus a two-year contract from Cingular), people have said that this phone is too expensive for the U.S. market. Although that's certainly cheaper than a smart phone or an iPod, it remains to be seen if the market will feel the same way.

I'll be purchasing two iPhones as soon as they're available: one for myself, to replace my Treo 750p, and one for my wife, to replace her Sidekick.

For more on the iPhone, check out the series of still shots at Engadget, which shows Jobs putting a phone specially wired to generate external video through its paces.