Auto tune kubernetes requests/limits? I know of ways to set up monitoring (e.g. prometheus/alert-manger) to notify me if kubernetes pod requests/limits are too far off actual container usage.

Are there any systems built to help you actually act on this information in some automated fashion though?  This may sound odd as I realize automatically raising a limit makes it... not a limit?

Having said that, it still sounds useful to be able to automate tuning across a large k8s environment.  This may be especially true during non-prod/staging when you're doing load testing and trying to figure out what the reasonable limits are in the first place.
Automating this kind of behaviour is a quite risky since you have ResourceQuotas usually set up as a constraint for a namespace and from there on the pods must be aligned with it. 
You might end up with a pod non being scheduled at all.