Something like this?:
@Override
public void onUpdate(ItemStack par1ItemStack, World par2World, Entity par3Entity, int par4, boolean par5)
{
super.onUpdate(par1ItemStack, par2World, par3Entity, par4, par5);
EntityPlayer player = (EntityPlayer) par3Entity;
if(player.getHealth() < player.getMaxHealth())
{
for(int i=0;i<9;i++)
{
if(player.inventory.getStackInSlot(i) == par1ItemStack)
{
player.heal(1);
break;
}
}
}
}