I am still looking for a wordpress plugin. The closest I found is WordPress Core Control, but somehow this is not “the one”.
What I noticed when played around this plugin was the following:
There are a bunch of FOR ME “unnecessary” crons running.
Twice Daily wp_version_check
Twice Daily wp_update_plugins
Twice Daily wp_update_themes
Once Daily   wp_scheduled_delete
Once Hourly wordbooker plugin
Twice Daily update_network_counts
Once Daily  akismet_scheduled_delete
From here I need the wordbooker plugin, but it is enough to run it 5 times a day, the askimet plugin once a week. Because I set up wordpress not to use Trash, the wp Scheduled delete is not necessary. The version check, theme update check and plugin update check would be again enough 1/week (IN MY CASE). So I would like to get rid of these extra crons, and let them run as many times as I want.
I searched for days for a plugin like this, and nothing to be found.
I will stick to a “middle solution”. There are 3 plugins,
that supposed to do (half the job), Because I don´t want these tasks “Off”, I want them to be much rarely.
This is especially annoying when there are a few other sites on the same host, and all of them keeping the server busy with silly updates.
There is a WP-Cron Dashboard to, I need to test it to see if it works.
There was a “WP Control” plugin, but the last update is from 2008. So I won´t install that on my site, because I am pretty sure it won´t work properly. Well… if I will have a bunch of time, I will maybe give a try.