Features

Utilizes the Pipebelts API to create a piped variant of every transport belt, allowing fluids to directly cross transport belt lines.
Underground belts utilize underground pipes as well.
There is currently no splitter variant (I didn't test extensively to see how it worked, but conceptually speaking, splitter-pipebelt didn't interest me very much. Might consider adding it if there is any request for it)

Notes

I'm honestly surprised nobody has made a mod with this functionality before, and especially surprised that the Pipebelts API doesn't have a single other mod that utilizes its functionality in any way.