This example balances the resources evenly across 3 belts:
![Image](https://forums.factorio.com/images/ext/a35b197d117ebaa8afb5b82720f0effc.gif)
It's still just an early version and there's some kinks. At the moment it will not function properly with a belt thats loaded on both sides, but I'm sure that can be fixed.
I'm sure I'm not the first with this idea, but I wanted to share it anyway.