With IPHost Network Monitor you can run simple snmp requests against a IBM device in your network.
ibmMvsTcpConnClientUserId
ibm Mvs Tcp Connection Client User Id
When the corresponding TCP connection is for a 3172 Telnet session then this object contains the Client's userid.
Back to ibm_mainframe-Mvstcpip MIB page.
IPHost Network monitor allows you to monitor ibmMvsTcpConnClientUserId on IBM device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring IBM Blade servers right now.