[ShadowMortar]

ALS hook SetPlayerHealth/Armour, GetPlayerHealth/Armour, and under OnPlayerTakeDamage do the thing.
Example:

PHP Code:

SetPlayerArmourEx( playerid, Float:armour ) {
    PlayerInfo[ playerid ] [ pArmor ] = armour;
    return SetPlayerArmour( playerid, PlayerInfo[ playerid ] [ pArmor ] );
}
GetPlayerArmourEx( playerid, &Float:armour ) {
    return PlayerInfo[ playerid ] [ pArmor ];
}
#if defined _ALS_SetPlayerHealth
    #undef SetPlayerArmour 
#else 
    #define _ALS_SetPlayerArmour
#endif
#define SetPlayerArmour SetPlayerArmourEx
#if defined _ALS_GetPlayerArmour
    #undef GetPlayerArmour 
#else 
    #define _ALS_GetPlayerArmour
#endif
#define GetPlayerArmour GetPlayerArmourEx