dont know if its too late now but try looking at this: http://forums.bukkit.org/threads/mcmmo-overall-level-chat-prefix.181492/
it's mcmmo that does exactly that kind of heart thingy but the one Lacrosse17 sugests looks verry similar :D...
thank you so much for the slimeblocker plugin ive tested it on my server and it works for me
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