Thanks david for your response. You are right that I am not going to get a very accurate depth map but thats OK. A rough figure is all I need.
My range can be anywhere from 0.5m to infinity, however the accuracy requirement goes down as we move farther. For example if something is in 1000m range then it does not really matter if it is 1000m or 10000m. On the other hand in the close range I would want to know if something is say 5m or 15m. But again it does not matter if it is say 4m or 6m instead of 5m. Basically You can say that I need an estimate at the level of what a human observer can guess by looking at the scene.
From playing around with my s95 at 6mm (Horiz FOV = around 65 degrees, Vert FOV = ~51 degrees), and looking at the focus distance info from EXIF file, I think the resolution of information should be good enough for my purposes.
So basically my main issue now is to automate the process instead of having to select each focus location one-by-one, taking a picture at each point and then parsing the EXIF for each file.