How to prevent accidental keyboard input in a Linux terminal

In a multi-monitor setup, sometimes I type in the wrong window without knowing and end up spamming WeeChat IRC.

To prevent that, I now use gnome-terminal and turn on “Read-Only” mode to disable typing. This useful feature is, however, not available in other terminals. Please share in the comments if you know of alternatives.

2018 Mar 27 UPDATE: xfce4-terminal also has a “Read-Only” mode.
2018 May 7 UPDATE: konsole too.