I've created this tool for picking gradients from screen. It's heavily inspired from the same one in Substance Designer.
For now it's working all right in Win, and it seems to work in OSX. As it relies on some platform specific features it's kinda fragile. Unfortunately I didn't have a chance to test it on Linux.
It also works as a color picker for color parms. To use it just right-click on the label of ramp or color parm and choose Gradient/Color Eyedropper.
The package with the tool is here: https://github.com/igor-elovikov/hipie [github.com]
You can either put it in your
$HOME/houdiniX.X
directory or install it as a external package (copy hipie.json to your packages and point to directory)