[Riraito]

hey that is a great idea, I definatly think its possible, you would probably have to create a bunch of heart frames , and hide/show them depending on how much hp you have

if UnitHealth("player") / UnitHealthMax("player) == .5 then 
    for i = 1,5 do
        getglobal("HeartFrame"..i):Show();
    end
end

etc.