Built this little app this past week because I was not happy with the current offering.
Compared to Greenify or other xposed modules:
1 - It's free 2 - Kills system apps/services 3 - Better design 4 - Way smaller memory footprint 5 - Runs every X seconds instead of only when screening off. All operations are done on the background thread so system interactivity isn't affected
This is not meant to be revolutionary - it's not an original idea - but I built it according to my own needs and what I think a app like this should work.
There's an option to purchase a "Pro" key, but you can also use all the features for free toggling the right option.