With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
clmgmtLicenseMaxUsageCount
clmgmt License Max Usage Count
1.3.6.1.4.1.9.9.543.1.2.3.1.10
This object indicates the maximum number of entities that can use this license. This object is applicable only if clmgmtLicenseCounted is true(1). The entity that is being counted can be anything and it depends on the licensable feature.
Back to CISCO-LICENSE-MGMT-MIB MIB page.
IPHost Network monitor allows you to monitor clmgmtLicenseMaxUsageCount on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco firewalls right now.