With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
natAddrBindCurrentIdleTime
nat Addr Bind Current Idle Time
1.3.6.1.2.1.123.1.6.1.11
At any given instance, this object indicates the time that this bind has been idle without any sessions attached to it. The value of this object is of relevance only for dynamic NAT.
Back to NAT-MIB MIB page.
IPHost Network monitor allows you to monitor natAddrBindCurrentIdleTime on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco mobile switches right now.