Lightning sensors (Stormscope) were integrated into the radar display and were specified as original equipment on Jetstream 41 aircraft that were delivered to BRAL/Loganair.
The reasoning was that these aircraft would be spending their flying lives at or below FL250, where there is a greater risk of strikes and were specified, not by "extravagent owners", as gengis put it, but as a cheap addition to assist crews avoid both lightning and cb activity, which are not neccessarily co-located. Pilots liked it too.
The commercial payoff was that there was a significant reduction in reported lightning strikes on the J41 compared to the ATP which was not equipped with sensors; thus less engineering time was spent on lightning strikes and their aftermath.
Because of this good experience, a similar fit was ordered on the EMB145 although Embraer took a little time to get it installed.
It was a cost and safety effective tool as far as we were concerned. Bit like the talking checklist really, but that's another story.