As far as misfire detection, they did use spark plug tip ion detection for a few years but abandoned it.

Modern car ECU's look at crankshaft velocity in order to detect misfires. Typically a 60 tooth crankshaft sensor reveals that crankshaft speed is not constant - it actually dips down during a compression stroke, and dips up during a power stroke. It's very interesting to look at the speed (ripple). The flywheel smooths it out a bit. Just looking, comparing peak-peak values.
But that crank sensor is likely not there and not sure how hard to attach one or find a gear.

Ignition Trouble Codes (DTC) are done by looking at primary voltage. An ignition coil is a transformer after all, say 1:85 turns ratio, so a max. of about 385V could ever be seen (disconnected spark plug, very bad).

You will first see the firing line, to inititate the arc (not useful) - then the burn.
If the arc voltage is too high (plugs worn, have too big a gap or resistor fail)
If the arc voltage is too low (low compression, plugs have too small a gap, insulation breakdown etc.)
If the arc time is too brief (problem with the igniter, short dwell etc.)
If the arc time is too long (problem with insulation breakdown etc. )

The burn time is measured. So you are looking at the spark energy (voltage and burn-time product) to see if the ignition system is within a window where all is OK, otherwise set an OBD trouble code including the cylinder #.


I think you could make a circuit (like a tach) that monitors coil primary voltage and gives you average (plateau) firing voltage and spark duration, all the while you are going for a drive.
Distributorless or wasted-spark systems would be a lot more work. It's faster to just swap out parts instead of troubleshooting sometimes.

 

Those SUN instruments are indeed good,
BUT neither small nor especially portable.

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I was being facetious, I guess it wasn't obvious enough,
"fixing" an Ignition problem is not really very practical.

All Ignition-parts MUST be in good working order,
if they are not,
they should ALL be replaced, at the same time, with brand-new parts.

Replacing one Spark-Plug-Wire is an absurdity.
Replacing the Distributor-Rotor, and not replacing the Distributor-Cap is likewise an absurdity, etc., etc..
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There are also lean misfires and valve float misfires that are not related to the spark plug. And on fuel injection systems there may be an occasional injector issue. And 2-stroke engines can have some unique problems of their own, related to tuned induction schemes. (motorcycle engines, mostly)