Sierra Automator KeyboardViewer App Shortcut
Thanks all! process whose frontmost is true and visible is true froze Keyboard Viewer behind a Finder window that also froze - 2 freezes in 2 days. Following seems to work quite well, in macOS 10.13.2. Simply add the delay 1. 

    on run {input, parameters}
        if application "KeyboardViewer" is running then
            quit application "KeyboardViewer"
            delay 1
        else if application "KeyboardViewer" is not running then
            activate application "KeyboardViewer"
        end if
        return input
    end run