Blender's Smooth Corrective modifier, a form of Delta Mush, reduces highly distorted areas of a mesh by smoothing armature deformations, but it only works inside Blender. Export an armature-deformed character to a game engine and the smoothing is lost. Corrective Smooth Baker from Mesh Online addresses this by baking the Smooth Corrective modifier into vertex weights, so the smooth effect stays with the exported character.
To do it, the add-on twists the armature to generate a large number of dynamic random poses and derives vertex weights from them, so the result fits any pose. You can watch the baking happen in realtime through a progress bar that reports the completed percentage, the completed and total vertex counts, and the remaining time.
In Blender 2.80 and later, the interface appears in the View3D sidebar under the Mesh Online tab once you select both the mesh object and the armature. Tutorials cover the basis workflow along with Auto-Rig Pro and Rigify setups. Mesh Online has also integrated this add-on into its Voxel Heat Diffuse Skinning add-on.