Imagine you can have a small (from 10x6cm or even less), light (~100g), possibly wireless (without WiFi) controller with 2 (or a bit more) physical buttons and one endless encoder with push function. And these controls can be assign to Reaper actions. And that controller cost under $10.
Or may be you want 100 buttons, possibly wireless, controller. Still for around $10.
You probably already have both!
These devices are mouse and keyboard. The REAPER extension is called "AZ Not" (... a mouse/keyboard).
To avoid confusion:
* the mouse/keyboard device used with "AZ Not" will no longer work as normal, it will work as a RAPER dedicated MIDI Control Surface.
* other mouse/keyboard will continue to work as usual.
Windows only, free to use, closed source extension.
The first alpha, not well tested yet
http://www.azslow.com/index.php/topic,423.0.html