Here's a video I just uploaded about it:
This is my first video, so I'll keep the description short here. I've been working on this mechanism to allow you to use a minecart w/chest to select your destination.
So the way you use it is to put an item in the cat w/chest. Each "stop" on the track uses a different "indicator" item, so you put the item in the chest which matches the exit you want to take.
For example if I wanted to send a stack of iron ore to my friend who's stop is designated by a Dandelion, I'd put one dandelion in the minecart along with the iron ore.
These indicator items can be used for anything, not just selecting a single "destination". For example, you could have one item for each "direction", and use that to control your path rather than a specific item for each destination.