Apple described the capability as useful for multi-player gaming, and demonstrated it with a backgammon game.

What's unknown at this point: How many people can you get on a single network? A handful? Dozens? Hundreds? What's the distance limitation? Can the peer-to-peer networking be used to relay signals -- for example, could my iPhone pass information on to another user located 10 feet away from me, then another 10 feet away from him, and so on until my information has traveled down the hall, out the door, and across town?

The peer-to-peer technology presents intriguing possibilities for business and other non-gaming apps. For example, salespeople could give on-the-fly presentations on multiple iPhones without having to huddle over the device with their clients. iPhone users could flip business cards and brochures to each other at conferences. I suspect the most interesting applications are things that I can't imagine right now.

Hardware APIs

With 3.0, Apple is broadening support of its APIs for hardware accessories. Until now, you've been able to buy third-party headsets, speakers and microphones to give the iPhone and iPod Touch more power. With the iPhone 3.0, you'll be able to buy a greater variety of devices that do more things.

Some of the demos at last Tuesday's preview event were for very serious applications: LifeScan, a Johnson & Johnson company, demonstrated a glucose monitor for diabetics that could take blood samples, check for blood sugar, and transmit the results to an app on the iPhone. Combined with data on diet and exercise inputted by the user, the application calculated a recommended insulin dose, and allowed the user to analyze charts of historical blood sugar data to calculate lifestyle changes to keep the disease in check. Likewise, Apple described a blood pressure cuff that kept track of the user's blood pressure. Both applications would allow the user to transmit data to doctors or, if the user is a child, his parents.