We have used with good success the leaf area meter (and conveyor belt
system) by LiCor. It gives all the variables you are looking for and
allows you to import the data into a spreadsheet quite easily.
We have also used hand-held scanners as well as flatbed scanners to
in-vivo measurements of leaf areas.
The image processing software that we have used for the latter is NIH
Image. It is free and allows you do some fairly advanced manipulations.
You can do a search on Lycos or Yahoo for the title and it will come up
with the address.