AnyConnect-logo  Cisco have now released a BETA AnyConnect client for Windows Phone 8.1 availible here  at the Windows Phone store
I havn’t tested the latest builds but the initial version had a few showstoppers that look like to have been fixed.  Remember this uses SSL/TLS encryption only and your local security policy may mandate the use of IPsec, along with all its issues !
Also they dont appear to have fixed the session timeout bug so that may cause a few headaches with disconnects.