With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
ccmPhoneStatusUpdateTime
Cisco Call Manager Phone Status Update Time
1.3.6.1.4.1.9.9.156.1.2.4.1.3
The time of the phone's registration status change.
Back to CISCO-CCM-MIB MIB page.
IPHost Network monitor allows you to monitor ccmPhoneStatusUpdateTime on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco routers right now.