The Luxrender devs. are already on the ball with implementing this (see the Mercurial log for the Lux. app itself)
http://www.cs.princeton.edu/gfx/pubs/DeCoro_2010_DOR/outliers.pdf
This could actually make unbiased rendering of complex scenes perfectly doable without having to wait for ages or needing to touch up in a paint program afterwards.
It basic removes outlying samples in sample space rather than trying to reconstruct pixels after a spot is altered like what bilateral blur, median filtering, and general noise reduction does, and as a result the image looks spotless with no lost detail (the algorithm itself could reduce brightness, but they mention that it can be corrected so no lighting is lost)
NOTE: This .pdf is only 12 megs so it shouldn’t take too long to download, but it is rich in comparisons.