When I was a teenager, this time of year would be insufferable. My bedroom would be nearly 90 degrees Fahrenheit without air conditioning, but it wasn’t even particularly hot outside. I had at least five tower PCs running inside my bedroom, all contributing a lot of heat to my tiny little room. Each performed its own role in my home network, with a file server, domain server, Exchange server, and media center PC among them. All of those tower PCs are now inside my pocket, thanks to the iPhone.