I recently received my Arduino Leonardo, and I have found out that I can make midi controllers with it but, I what I wondered was, can I make a controller that interfaces with Ableton. What I mean is that there could be, say, a record button and a play button that activate said things in Ableton without prior midi mapping or, maybe a session view, like on the Akai APCs or Novation Launchpads. Ideally, I hope to make something like a simpler Launchpad Pro or Ableton Push.
You'll have to midi map it. Or write some glue. The push and the APC have some glue programs written in python that connect the devices to Ableton.
Google 'abelton control scripts.'
Both the Akai and Novation controllers use the MIDI protocol, but they seem to be using a proprietary handshake.
The support section of the Novation site has a document with the MIDI implementation. If you implement it like this, it might work without the handshake. If not, you could write your own script, as mentioned above.
You might be interested in my MIDI Controller library.