There are a few technology i dreamed of when i was a teen, or anywhere from 30 to 10 years ago. Some of them have become realities today.
Most of these have become realities today.
Wikipedia is encyclopedia at your fingertip, and more generally, the internet. Even just 10 years ago, any fact, even trivial ones, such as list of US presidents, means a trip to the library. To answer any trivial question, it means plan and drive/walk to a local library, then “do research”. It often means that to answer a trivial fact takes at least half a day. Today, the answer comes within 5 seconds, from the multi-purpose phone device in your pocket.
Google Earth and Google Map is the realization of world's photos at your fingertip. For any place on earth that's well populated, you can immediately see thousands photos of it. The streets, the people, within few seconds.
For 3D models, Google Earth does some degrees of it. And Second Life also some degree. In Google Earth, all major cities have 3D models, albeit a very sketchy one. You can view any big city or building from any angle. Although currently the models are very rough sketches, basically just blocks of rectangles or spheres that lets you get a sense of the building's shape.
in Second Life, and in general 3D games, there you have the full detailed 3D models. With gaming software, you can actually walk-thru in it. Suppose it's a cathedral. You can walk into the building, walk thru any of its doors, corridors, hallways, basements, as if in real-life. You can also view the whole thing from any angle or position, as if you are a bird. Though, the problem with Second Life or 3D game here is that only a handful cities or real life buildings are available. Vast majority of scenes and buildings in 3D game are fictional, great by itself, but has no educational values in history or culture or real architecture.
The good aspect of Google Earth here is that ANY major city or building are available. The good aspects of 3D games is that you have detailed, walk-thru model, but just a handful of them.
Detailed walk-thru models as in gaming for all buildings and terrains of the world is probably coming, perhaps in 10 years?
As for any video on demand, it has not happened yet. Today, you can view most popularly demanded items, such as movies (but usually with payment). However, if you want to see for example Olympics games of a particular year that's been recoded on video, good luck! Or, any news broadcast program of a particular year and day, it's nearly impossible, paid or not. I suppose, they will eventually come. 5 years? 10?