I have a Kindle 3 and I want to do the same thing. Using this page:
http://blog.diannegorman.net/2010/09...ortcuts-et-al/ I was able to find my kindle 3's sim card, serial number and even phone number. When I call the number (found on the 3G modem info screen), a females voice comes on and says "not a valid number" then hangs up on me.
Has anyone tried figuring out the whispernet protocol?