I don't know if there are any other games that do this, it feels like something that should be a part of an OSR game because it uses a lot of the tropes from that field of gaming. Maybe there is, maybe it's new.
Here's the idea.
One of the issues I have with hit points in most D&D and OSR games is the idea that every level, hit points go up, and up and up. You start gritty and fragile, one or two strikes can take you down. Eventually you get to that level 4-7 sweet spot where combats take a little longer, where special powers become available, and where characters start to feel like they can make a difference in the world. Then you transcend this point, combats become a boring slog, roll after roll to whittle away one another's pool of hit points, weapons still do the same damage on a strike but it takes so many more of those strikes to inflict significant impact.
I'm looking to remedy this a bit.
There's a school of thought which states that hit points reflect combat prowess and ability to dodge or absorb the worst of any incoming strikes. But if it represented this, why wouldn't hit points be modified by dexterity. Since hit points are based on constitution, they are more clearly an analogue of the physical wellbeing of the individual... this is backed up by the idea that poisons, diseases, fall damage, and other types of non-combat injury all work with the same hit points that combat does. Some newer games have circumvented this by introducing "ability score damage" in which specific creatures are able to ignore hit points. I used to do something similar, where critical hits didn't do double damage, but instead inflicted an equal amount of damage to hit points and Constitution (where a complete loss of Constitution resulted in instant death).
Instead of that, I'm now thinking that characters should simply have hit points equal to their Constitution scores. An average of 9-12 points, with less than a quarter of the population having fewer than 8, and less than a quarter having more than 13. This resolves the issue of starting characters being too fragile, and the issue of high level characters being too resilient.
Instead of hit points being a direct pool use for absorbing incoming damage, they now become a pool of energy used to replenish that Consitution pool. This happens when characters have a short rest, while the hit point pool gets replenished by eating food and taking long rests. Wizards and other magical characters still have the issue of low hit points, meaning they don't have a large pool of reserves to restore themselves (they do it through magic instead). Fighters and Barbarians do have significant pools of reserve health, if they get the chance to take a breath they can come back to a conflict with a second wind. Other character types fall between these extremes.
There's more in this I'm sure, but as a system idea it seems to address a few of the problems I've seen arise regularly.