Plugin for changing content based on visit behaviour

Hi All,

I’ve done a bit of searching, but im just wondering if any one knows of any plug in that will change content based on users behaviours, or another one that can change content based on keyword.

I.e. rather than saying hello, when a visitor comes back it says “welcome back”

and when someone searches for “cheap phone” it will show content based on price, if someone searches for “direct mobile phone limited” it will display content about the company in the same place that the cheap phone content would have gone?