As you start brainstorming your own visual tooltips, do keep in mind these caveats about the example outlined above:
1. The data marks under the tooltip sheets won't be sensitive to mouse hovering. In other words, the tooltip sheets have to be carefully positioned.
2. The technique is suitable for dashboards with relatively sparse data marks.
3. The positions of the visual tooltips are fixed.
4.When the user hovers over one data mark, the frames of all tooltips will briefly light up. This is is a transitional effect. If possible, lay the tooltips sheets on top of each other like in the Ambassador viz as a way to minimize the effect.
5. You can either turn off the regular text tooltips or use them alongside these visual ones.
There have been other options to put visual charts directly within Tableau's tooltips. Here's a Knowledge Base article on using bars in tooltips. And this VizWiz guest post by Rody Zakovich is also a great example.
Last but not the least, I would challenge you to come up with vizzes using the technique described here. Let me know what you come up with in the comments below.