Many years ago, Powley made a device that was mounted in place of a rifle scope. It had a sliding mass that crushed a lead pellet. I don't think it worked out too well, given the variables it didn't take into account.
About 10-15 years ago, Steve Faber marketed a simple peak reading strain gauge system. It gave an answer in microstrains. That is easily converted to pressure with the Hoop Strain Equation. I still have that around somewhere.
I built myself a dual trace strain gauge system a few years ago, so that I could simultaneously see what was going on in two places in the barrel. It gave two graphs, and, like Steve Faber's device, did not have the strain to pressure conversion built in. Sadly, it didn't reveal anything earth shattering. But it was fun.
As long as you are operating below the plateau point, where more powder increases variation but not velocity, your chronograph is as good an indicator as you are likely to need. MV is VERY highly correlated with peak pressure.
