I think tmux's scroll mode (ctrl-b [) is similar. You move the cursor freely and if in vi-mode, you can us vi commands (as if in visual mode) to select and copy (y) contents. Pressing 'enter' goes back to non-scrolling mode, and then you can paste the contents with the configured tmux keys.
> You could then press a "copy" key and it would copy one character at a time from the second cursor to your current editing position
Each time you pressed the "copy" key it would literally advance both the main cursor and the copy cursor by one character, with the copied character appearing under where the main cursor just was. To copy multiple characters you would need to press the copy key multiple times or hold it down to trigger autorepeat (even then you would see this process gradually happening until you released).
