This is an example implementation using this module.
You can either clone this git repository and run this yourself if you got node.js installed or download prebuild packges here
To use this you just have to start the .exe file inside and go in to your game. To change the displayed summoner names you can either click on "Fetch Summoner names" in the menu bar to automatically set the summoner names or you can use "Toggle editable summoner names" to make change them yourself. (Don't forget to press it again after you are done changing the names so you dont accidentaly change them afterwards)
To reset the application simply press Ctrl+R or reopen the application.
This is how the application looks. It got every feature you would expect from the normal spectator. To change something you can edit the html or css files.