Somthing like that should be possible code and details might vary...
lang=python
import mitk.plugin
import mitk.core
import SimpleITK as sitk
nodes = mitk.plugin.get_current_selection()
for node in nodes:
image = node.get_data()
gaussian = sitk.SmoothingRecursiveGaussianImageFilter()
blur_image = gaussian.Execute(image)
node.set_data(blur_image)
After execution content of all selected nodes are blured and the render windows are directly updated accordingly.