A list of possible SMS gateway providers:

http://www.qwasi.com

http://www.bulletin.net

http://www.upsidewireless.com (reportedly used by UCLA libraries)

Reference Sites:

http://www.schneier.com/blog/archives/2009/05/secret_question.html

http://www.networkworld.com/news/2009/051909-study-secret-questions-dont-safeguard.html

http://www.technologyreview.com/web/22662/

http://www.walyou.com/blog/2010/09/20/facts-about-text-messaging/

http://blog.seattlepi.com/microsoft/archives/223036.asp?from=blog_last3

http://cellphones.org