Check Open Flash Chart 2:
http://teethgrinder.co.uk/open-flash-chart-2/area-line.php
When you hover the mouse near the line, it shows the anchor value. Currently, fusion charts area, it's very "cryptographic" to the client. There's no way to know where the "peak" is, nor it's easy to tooltext tip it. On an almost plain area, it's impossible to know where the variations are. Maybe I'm missing a parameter on FC, but so far I couldn't find it.
Maybe I'm searching for the wrong feature name, calling it "snap to anchor", what would it be called? (I'm Brazilian btw)