Not having access to any 3D scanning I decided to do some basic surface mapping the long and tedious way and came up with this tool to use as a template.

The grid holes are spaced 5mm x 10mm and each hole measures 1.1mm x 4.1mm which should allow a fairly snug fit for the "depth gauge shaft" of my Chinese made electronic digital caliper to pass through.

Yes, I'm fully aware that this will be a very time consuming method of mapping a surface but at least it will be reasonably effective.

[EDIT] I used this tool and a digital caliper to "map" the contour of the back of my HTC Desire HD phone so I could make a tri-pod mount for it - http://www.thingiverse.com/thing:8039

I just did one half and then mirrored the measurements for the other half.