I was reading an Instructable on building a Lightning Detector but the sensor alone was $25. Then I stumbled across a ready made device for $24. This looks like one more thing to stick on my panel. It detects lightning 25 miles away. It seems to display distance from the lightning, but that's probably only based on intensity of the strike and not a true distance.
If you don't know this about lightning, first there is no attraction for lightning to hit your plane. You just got to be in the wrong place at the wrong time. Second if you do happen to be in the wrong place, our planes are non-conductors. This means that there is no path for lightning to travel. This means if you get hit, your plane will basically explode in the air. This is why I stay far from thunderstorms!
ADS-B with ForeFlight (Apple) does display lightning but if you don't have that, this device below is a good option.
Here is an ebay link for the best deal I've found so far.
Mike Q200 N3QP