We are creating a concrete shell spa and want 4 jets with independently controlled air induction - one air induction control knob top-side per each jet. We're planning 1/2" PVC from the control knob/valve down to the jet area.

We see posts about check-valve problems leading to jet body replacements
required sometimes ... we don't want to embed any jet body needing maintenance in the 8" thick concrete spa shell, but we do want a check valve to prevent water spurting up through the air induction control. We also want air bubbles in the jet output.

Can you recommend a jet and jet body and check-valve we might use? The
idea of a simple directional eyeball type jet would be fine, but I wonder if we need a jet which specifically mixes the air & water, or does suction past the air input pipe draw air in bubble form through and out the jet?

Of course willing to purchase all parts at SpaPartsNat and give it a try with a few experiments ... any advice?

You don't need an air check valve, there's a venturi created inside the jet, so as soon as water passes through it, it creates a vacuum. I wouldn't bother with an air blower plumbed into the afc or h20 plumbing either. The jet you're describing is virtually every spa jet, nothing remarkable about it
Just keep the air lines separate.

Additionally, your 'air control knob' has a check valve built into it.

like this one: http://spapartsnet.com/Air-Knobs-Valves ... 7_0_1.html