I just invented something in my head right this second.
It's a perpetual PV that recharges itself by the vapor you exhale. So, like there'd be a tiny windmill inside the PV to convert the energy.
It'd be super stealth, since you wouldn't see the vapor plumes. (When I first read about "stealth
vaping" I thought actually that's sorta what it meant, that the PV sucked back in the vapor so you wouldn't be looking like a fire-breathing dragon).
I am genius. Give me my million now and I'll be on my way.