Other small internet devices are in the works, some already on the market. None approaches the full benefit of a PC or Mac or Linux tower.
The iPhone has shown the way. The iPhone is proprietary and limited. Another important device is the Nokia n800.
These new devices need an underlying technology to work. Google has just announced Android; Symbian is already available, such as for Nokia devices, the iPhone has its own proprietary system, and Windows also has a system. These are operating systems.
All that just means that things have not quite settled down yet.
However, more and more small PCs or "netbooks" are becoming available, and a few even small PC tablets are out there.
The Nokia N810 demonstrates what is coming in a very small device.
You should be very comfortable with computers to use it, however, and very comfortable with a small keyboard. Most of all you should have good enough eyesight to use its small 4" screen.
With that in mind, wherever there is wireless internet you have all the functions of computer and phone. This includes even the ability to watch and remotely operate TV, remotely operate your tower, access its files, access FM and internet radio. The last requires tinkering, though. The device has limited GPS.
The device is primarily an access device. Although it has a keyboard, input such as word processing is demanding. There is also no printing and no external screen, capability. You could print remotely through your tower and your tower could display its screen, however.
Additionally, more and more software, much of it from Google, runs from the website and not from the device. A powerful computer is no longer needed to run more and more applications. In addition, Google has more and more applications designed especially for the small screen.
The device software is extremely reliable.
You can explore applications here which are automatically downloaded and installed from the site:
Click here: http://maemo.org/downloads/OS2008/
A larger, but still small, PC is the EEEPC.
The Nokia N810 is 8 ounces; the EEEPC two pounds.
Expect more devices to follow.
The newest Apple iTouch is now much expanded in its capabilities.