This script for the Scriptable app creates widget backgrounds that appear to have a translucent blur effect. It's based my original transparent widget code, but it adds the ability to emulate the light or dark blur effect used in the Batteries widget from Apple.
Before you start, go to your home screen and enter "jiggle mode" (where you can move apps around). Go to the home screen on the far right, which has no icons in it. Take a screenshot here. You'll be prompted for this screenshot when the script runs.