Some more comments...
I could not find a spec for the response time of the Comp-Peek, but it seems like both units probably use the same class of transducer, because they both have the transducer buried in a box with amplification separate from the basic transducer. Those transducers are about $60, so you could make this a DIY project building your own amp and using a GP scope fairly cheaply. There are transducers with built-in amps, for about $75, but their response time is about 1 msec vs. the 100 usec of the Pico (and C-P, I think); 10x slower. The transducer shown in the video of your reply #23 is probably the slower "self-contained" type.
What makes the Pico so much better, is it the software? If so, then forget the DIY approach; anything you do with a GP scope is probably going to seem cumbersome in comparison to SW specifically for this purpose; would probably seem "light yrs behind" even the C-P.
None of this is a new concept, of course, I have a 1930s textbook showing similar "indicator cards"; but they also include the combustion pressure to get the whole cycle.
There is often discussion on performance sites (like Megasquirt) about using transducers to show the whole cycle (combustion included), and I have toyed with cheap ways to do that, like a specialized spark-lug or thin "banjo" fitting/gasket under the plug. However, pressures in the cylinder doesn't tell the whole story. You have to integrate the pressure over all the crank/rod angles to determine net torque at the crank, and account for the varying friction from side thrust on the piston. I think it is far easier, and more accurate, to just go to "the bottom line" and measure torque with a dyno.
Again, for diagnosing VVT, I can see that seeing those pressures, even without combustion, can be quite valuable. Maybe for variable inlet runners, too, but I think effects there will be more subtle and harder to see.
