Recently a customer asked if it was possible to consume SPS webservices to authenticate on SiteMinder through biometrics. They already have some applications that authenticate the users on SiteMinder using biometrics, so in their mind it would be easy to translate it to webservices. It's not.
I opened a case #00016297 asking that but it's really not supported and will not work.
So, I'd like to suggest that functionality for the coming versions, but I don't know if it's technically possible.