>Being able to stream a collections of bytes (and collections of collections of bytes, recursively) is one case that I find myself wanting when sending data between programs at the command line.

If you don't mind using JSON as intermediary format, you might like to have a look at jq: http://stedolan.github.io/jq/

jq can also convert raw (binary) data to JSON objects containing strings (and vice versa) for further processing. Naturally, jq filters can be pipelined in many useful ways.