These features were once in Minecraft, but were removed.
List of Removed Features
Cameras were added as a way to take screenshots in-game. They were only accessible through inventory editing and were removed in Update 0.9.0.
It was stated it may be re-added with a proper image sharing system.
Nether Reactor Cores are just what the name implies: the core for the Nether Reactor. They were removed along with the exclusion of the Nether Reactor.
Glowing Obsidian is what the Nether Reactor Core reifly turns into when activated. Since it was a Nether Reactor related block, it was removed due to the Nether Reactor being removed.