It's partially visible under Monitoring>Sessions in Horizon Administrator. The MAC address if available will be listed in the Client ID but it varies based on the client (e.g. zero clients show a MAC Address while the Horizon Client will show a more generic ID which I'm not sure if anything can be pulled from).
For what you want you would probably be better off logging the data captured in the registry under "HKEY_CURRENT_USER\Volatile Environment\1".
