The chip outputs the number, energy and estimated distance of the lighting it picks up as register values which can be read via the I2C or SPI interface. So you could read those and process them and output to a display or (eg) a PC. Seems to me that this would be better done by an MCU Max, but I'm no expert on FPGAs - what think you??
What an intriguing little chip! Just had a look at the datasheet. Someone had to do a lot of homework to come up with that, I reckon.
I note that the antenna for it is tuned to 500 KHz, way above the Audio band of Max's unit, but then they are intended for different purposes. The IC claims to be able to reject noise from man-made souces like motors or fluorescent lights, so I suppose that frequency is where you'd get the most information about the lightning.
I work for an energy utility and we have a link to a "Storm tracker" site which records lightning strikes - I guess it would use something like this.
I worked on a sferics reciever with a friend in the 60's. We used a long whip antenna and a pair of coils mounted at right angles for the antenna. The direction of the storm could be discerned by the two phases (from the right angle coils)with the whip output channel setting up the reference for a crude phase demodulator. It worked pretty well. It seems like the circuit would also work for locating non directional beacon transmitters if tuned correctly.
I'm not aware of any kits for something like this (maybe I should produce one...) but really if you refer to the article (thru the link above) and go buy some stripboard and the components, there's not a lot more hassle than getting a kit.
The trouble with this circuit is that if it's anywhere near anything electric or electronic it picks up interference. But Max said that he had it next to his computer and it didn't pick up much, maybe today's PCs are too fast to generate much audio? But you could feed the output to an FPGA with DSP capabilities and generate a spectrum display on-board?