Tooltips like Twitter for Mac or Sparrow

I am trying to create custom tooltips like the ones found in Twitter for Mac, or even Sparrow. Do you have any direction for achievin开发者_StackOverflowg this?

Thanks in advance for your help,

Regards,

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Maybe you are looking for MAAttachedWindow?

http://mattgemmell.com/source

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Those tooltips are provided by Growl