MidiFire

(From the App Store description) MidiFire is a free-form, modular CoreMIDI router, processor, monitor and clock source.

App type: App

App store link:

Developer: Audeonic Apps

Developer AB Forum Handle: @Audeonic

MidiFire is primarily GUI based, but also includes the scripting language found in the Streambyter AU Midi plugin. As of version 2.0, MidiFire can host AUv3 MIDI effects. The help section has an updated manual.