Hi Manuel,
Per Boe an F5 FSE and Jason Rahm from DC, posted a solution on using APM to implement an SMS based one time password solution:
One Time Passwords via an SMS Gateway with BIG-IP Access Policy Manager
http://devcentral.f5.com/Tutorials/TechTips/tabid/63/articleType/ArticleView/articleId/1086432/One-Time-Passwords-via-an-SMS-Gateway-with-BIG-IP-Access-Policy-Manager.aspx
And George Watkins has something related for LTM and Google soft tokens. I believe this will require the advanced client auth license.
http://devcentral.f5.com/Tutorials/TechTips/tabid/63/articleType/ArticleView/articleId/1086517/Two-Factor-Authentication-With-Google-Authenticator-And-LDAP.aspx
Aaron