This is one of the major things that JuiceDefender on Android phones did, though...

fencepost on May 26, 2015 | parent | context | favorite | on: The mystery of the power bank phone taking over Gh...

This is one of the major things that JuiceDefender on Android phones did, though the app has apparently been abandoned (last updated more than 3 years ago). I suspect that there are newer apps doing the same things, at least on rooted phones.