This may be the single biggest opportunity area in LED lighting. High-energy-efficiency T-lamps (fluorescent tubes) are the lamp of choice in most every office building in the world. LED T-lamp replacements often require rewiring of the fixture. This is a barrier to adoption since a licensed electrician is required for this step while simple lamp replacement can be easily done by maintenance personnel.
Drop-in LED T-lamps are available and many do not have active electronics since the fluorescent ballast is already a current source. This works as long as the LED string current matches the ballast current.