few notices

[szepeviktor]

Please consider arranging the README into numbered steps.

use dirname() as in WP
require( dirname( __FILE__ ) . '/wp-blog-header.php' );

move './wp-blog-header.php' into a variable - maybe someone installed WP into a subdir
wp_blog_header_path = dirname( __FILE__ ) . '/wp-blog-header.php';

detect redis server
If you do not have Redis installed on your machine this will NOT work!

please consider changing the $websiteIp etc. block to defines (or an array) at the top of index-wp-redis.php with some comments
and write a simple php-cli tool to create that block

Is it possible to run your plugin later like in wp-config or in mu-plugins?

[Larceniii]

I tried mu-plugins and got a white screen. Found out it was due to the path to "wp-content/plugins/wp-redis-cache/" being hardcoded into the plugin, which is odd, considering the readme says the plugin part was optional.

With a little cleanup- this might be a pretty good thing to have.

[RobWiddick]

I've made a few of these changes as they were good suggestions!