When you first drop a wireless router into your house, you create a local area network (LAN). For most folks, the purpose of the LAN is to give each device in the house access to the Internet via your wide area network (WAN) provider. The LAN device talks to your cable modem, DSL device, or other hardware that connects you to the WAN and then the 'net itself. Facilitating traffic among the devices within the house is generally not considered.
That's been pretty much the case in our house. Sure, I have a server in the basement that backs up my desktop and hosts my website. We also use the LAN to move files from computer to computer. But, until about a week ago, there was nothing that really spoke to the potential of a networked house. It started with the simple thought: I have over 5000 high-quality music tracks on my Mac. Instead of playing them through headphones, how can I play them on the home theater system? It's got to sound better with Bose speakers and a couple hundred watts per channel. The second thought was: There are jacks I can use, but I don't want the computer in the family room. Here's where it starts to get cool.
About six years ago, I bought a first generation Apple Airport Express to use as a portable wireless base station in hotel meeting rooms where there was a wired connection but no wireless. When wireless became common, the base station went into a drawer. Apple built a couple of interesting features into the device. It can function as a wireless access point, or it can join an existing wireless network and function as either a print server or a music output device. Yes, it has both a USB port for connecting printers and a standard audio jack for connecting speakers. I reset it from access point mode to music mode and plugged it into one of the unused inputs on the theater system. The next time I started iTunes, I selected "look for AirPlay devices". As soon as I clicked "apply", the Airport appeared on the list of speakers. Check. And my music was playing in the family room. And then it got cooler!
The last thing I want to do is run upstairs to change playlists, pause the music, or hunt for a particular song. Enter the Remote Control App for the iPhone. This app uses connects iTunes and iPhones on the LAN. After a few setup steps, I have full control of iTunes, through the usual iPod look and feel, from the family room.
Circling back to the topic at hand, there's nothing involved in this that uses the LAN's connectivity to the Internet. The LAN connects our iPhones, our computers (both Windows and Mac), and our stereo system. It's not the smart house of the future or the flying car that the Jetsons promised, but it's a pleasurable step in that direction.