There is a mod called ChickenChunks for Minecraft 1.2.5. It's created by the same fellow that has created Not Enough Items (NEI). It does seem a bit more advanced and better than the ones already included.
I'ld really like to see this included with Tekkit instead, and hope for once that we have a proper chunk loader solution.
Source: http://minecraftforum.net/topic/909223-