Neat. I'm surprised this hasn't been done before (assuming it hasn't)

One feature I like about rlwrap is the persistent history.

It might be nice to build this into Linenoise as an option, rather than having to roll your own for every tool you use it on.

Antirez: if you think it's a worthy feature I might be willing to submit a patch. I think I might use this for the Narwhal and Objective-J REPLs.