(this is very rough, but still fine-tuning it to be balanced)
As that I run a low magic world, Cure Light Wounds, potions and the like are very uncommon, if not all-out rare (I cannot think of a singular instance where a PC has had access to Cure Light Wounds or found a potion of healing in the past 5 years of the game). In order to suppliment PC health and recovery so that foes do not have to be heavily revised from the Monster Manual, I've created a new system for healing. Please feel free to offer constructive criticism or other suggestions to streamline this system.
Hit Points
Hit Points are a measure of endurance and the ability to withstand glancing blows during combat. While HP continually rises as a character becomes more battle-hardened (leveling), Constitution does not rise. It represents the value of what a person can withstand before being eventually debilitated with Grievous Wounds.
Binding Wounds
Inuries can be treated easier using the Healing ability. This can be anything such as removing arrows, binding a wound from a blade, treating a bruise, taking a moment to catch your breath, etc... To treat a Hit Point injury, the player must make a Healing check at a DC versus the total amount of damage taken. This is a full round action and invokes an attack of opportunity. Treating an injury recovers the recepient at a rate of 2d4 plus half the roller's total Ranks in Heal, rounded down). It can only be done once per combat, meaning wounds suffered in a single instance of battle can only be treated once within a 24 hour period (e.g. Tordek has 7 ranks in his Heal skill. He can effectively heal 2d4+3 HP for anyone he binds).
Drinking Water During Combat
Water can be drank during intense duress (meaning combat) to immediately recover 1d4HP. This mannor of recovery can only be used during combat, is a standard action and invokes an attack of opportunity. A normal waterskin can hold 4 uses of water for recovery.
Eating
Eating a full meal can help recover HP as well. A poor meal mends 1HP, a common meal (or rations) heal 1d4 HP and a good meal 2d4 HP. It takes ten minutes to eat (this does not take into account preparation time). A meal can only be taken 3 times a day.
Resting and Sleeping
Sleeping results in a recovery of 1HP+ Constitution bonus, if any, per hour.
Constitution as Shock Value
Anytime a single attack exceeds the total Constitution score (Shock Value), a Fortitude check must be made at the DC of 10+ the damage taken. If it is failed, the player takes a Grievous Wound, suffering a temporary 1 point Ability point loss to his Constitution. Grievous Wounds are represented as major wounds (such as broken bones or deep wounds). These wounds are recovered at 1/day normally. Sleep does not increase natural mending of Grievous Wounds
Death
Death occurs whenever the player loses all his Constitution points. Once Hit Points reach 0, the player will fall unconcious and bleed at the rate of 1 Constitution point a combat round. They can be treated by binding the wounds at 10+ the total number of Constitution points lost. This stabilizes Hit Points at 1, and any Constitution lost recovers at 1/day as stated above.
QuoteA meal can only be taken 3 times a day*
*Do not operate heavy weapons after taking a meal. Do not combine a meal with alcohol, this could result in liver damage. Side effects may include sluggishness, stomach irritation and pains, bloating and gas. Please consult with your cleric before taking a meal.
I'm sorry, it just read funny when I read that line. Sounded like you were taking a pill. Now for real comments.
Binding wounds:Not bad. Do you have a class/feats which would heighten the character's ability to treat wounds?
From the text it seems that you would be able to provide aid during a battle. What happens if a healer binds the wounds of a person during combat, then said person recieves more wounds. Are the wounds recieved after the initial binding able to be bound or does the person have to wait 24 hours.
Are further attempts allowed if the first healing check has failed? Or do they have to wait 24 hours? Can someone else perform a check if the first person failed? Can someone else perform a healing check if the first person succeeded?
Water:The stipulation of only during combat, makes this ok. Otherwise characters would find the nearest stream and open their mouths. 1d4 isn't great, so it isn't overpowered. (though you may have one character bring 20 waterskins into battle :P )
Meals:These seem to be on par with water. An ok way to get back hp, and the limitation keeps it in line.
Resting:By the normal rules you recover HP after sleeping equal to your level. Up to level 4 or 5 yours may gain more hp for a character, but after that the normal rules would gain more hp after sleep. Maybe something like 1+ 1/2 lvl (rounded down) + Con bonus.
Edit: nevermind I missed the per hour. Though the VP/WP system in the srd does recovery at lvl/per hour. Constitution as Shock Value:Up to this points everything has been about recovering HP, now your talking damage. Have you seen the Vitality and Wound points system in the SRD and other systems? Raelifin uses this system and in the game that I played in his setting, it was quite fun. (His setting is low magic, low technology, and very fun). Con scores aren't going to be that high, so you are going to lose more Con scores because of a strong fighter using a masterwork greatsword is going to be doing 2d6 + 1.5 STR bonus + weapon focus feat tree. It won't be hard for him to be crushing bones of his foes with every swing. Unless he goes up against someone with an outrageous CON score(18+).
Death:Again look at the VP/WP systems (http://www.d20srd.org/srd/variant/adventuring/vitalityAndWoundPoints.htm) out there. They may be exactly what you are looking for.
Yeah... I use VP/WP (albeit modified) too... works well enough for me. Still I can almost see substituting real CON damage for Wounds, which could be awesomely brutal...