I quickly coded a small utility for Ableton Live that allows mapping of controller buttons / keyboard keys to increment / decrement tempo. There are other ways to achieve this (e.g. https://www.ableton.com/en/articles/tempo-mapping-buttons/), however for those with M4L this seems easier and more flexible. It’s obviously not very generic, but can easily be modified to increment / decrement other live parameters in a similar way. Just drop it on an empty MIDI track and map the two buttons.

Download it for free here: http://www.maxforlive.com/library/device/2986/rmx-tempo-adjust