Hi Jay,
The checkpoints are stored in a hidden directory on the flash. A combination of "show checkpoint all" and "show checkpoint detail " in each context will show the contents.
You could put together an expect script to iterate across all your contexts and "show" the files to some other network location. The recent discussion on backup scripts would be a good starting point.
There are probably good reasons why Cisco don't want to expose the location of the checkpoints.
HTH
Cathy