If you are using the AnyConnect client, depending on the version, it will send some attributes across in a CiscoAVPair that may help profile the device such as the platform, MAC, etc.
Here's an example of one connection from my lab that was successfully profiled as an Android:
mdm-tlv=device-type=LGE VK815,
mdm-tlv=device-platform=android,
mdm-tlv=device-mac=78:f8:82:c7:c0:b2,
mdm-tlv=device-platform-version=5.0.2,
mdm-tlv=device-uid=0105C3527987AEB4EBDD170CE15560E4A272DD14,
audit-session-id=0a1bfe010002000056c3aa9f,
ip:source-ip=70.194.74.193,
coa-push=true