Firmata C++ library for host?
openFrameworks appears to have this capability. It's written in C++. 

From openFrameworks - Communication:


  Arduino and other serial devices communication
  
  The communication module has classes to communicate with other devices
  by now through the serial protocol. This mainly allows to communicate
  with devices like the Arduino. There's 2 classes in this module,
  ofSerial which allows to communicate with any device through the
  serial protocol. It can be used to send custom commands to for example
  an Arduino sketch that will receive them and do something in response
  like turn an LED on, move a motor... It also works the other way
  around, you can send messages from the Arduino (or any other serial
  device), for example the read from a temperature sensor to
  openFrameworks.
  
  The second class, ofArduino, is specific to the arduino, it uses a
  protocol called firmata to send messages to and from the arduino that
  way you don't need to care about implementing the communication
  protocol from the Arduino sketch to openFrameworks and viceversa but
  instead you can just send and read values directly to and from any pin
  in the Arduino.