In reply to SonicXT's request,
I don't know how to show this in HUD or elephant; however, in some software like Tournament Indicator, you can see the WSD% and WSDW%. I find these two give me a better estimate of how likely someone is to call an all in on my part. Although, i usually use this to maximize my hand's value.. For example, when i have the nuts, or very close to it, I will glance at these two. The problem with a 'did not fold after flop' is that it will show the same stat for players that are quick to call and players that are tight but are very firm about their hands.
For example, a tight player that has seen 4/4 hands to showdown, when he is on a lucky streak and sees 4 really nice hands, would have a DNF% of 100, but his WSDW% would be 100 warning you that he has not been called on a bluff yet, and if he has he has managed to always win.
You may not really need both stats to get a read on their 'willingness to call'. I've considered just multiplying the two to get a WC%; however, I don't own software to make such a change. I'd love to see something like this in Elephant.