[Request] Conveyor introspection

[ZorbaTHut]

I'm trying to make a mod that gives some information about the items that are passing by on a conveyor. Unfortunately, it seems like I'm sharply limited in what I can find out about conveyor contents; at best, I can get what's basically an inventory view of the conveyor, which doesn't let me determine which items are moving on and which are moving off.

I'd like either a way to get object unique identifiers from a conveyor, if such identifiers exist, or a way to get the exact positions of items on a conveyor tile.

The end goal here is to create a "throughput combinator" that tells you how many items/second are passing a certain point; with either of the above options I can figure it out, but at the moment it appears impossible.