im looking for a spectator plugin. Can you help?

Im looking for a plugin. This plugin is for spectators, that if they are really spectating and not afk they have to press 1, when a window shows up. Ive seen this on a few servers. i would like to add this to mine. Ive tried looking for it, but no luck. Can anyone help me, like give me a link or a place i would mostly find it?