I need to generate a notification for APs that have lost connectivity so that we can proactively dispatch a tech to troubleshoot. We have about 150 APs on our controller. Looked into Cacti and PRTG, but they don't seem to be able generate notifications for the subordinate "objects". I have looked into Zabbix, but haven't been able to spend the time to learn it yet. Any suggestions?
If you're open to a commercial solution, SolarWinds has a fairly good wireless monitoring portion in its Network Performance Monitor product that includes a pre-built alert for thin AP's going down.
Some information on its wireless monitoring is here.
As @Mike Pennington suggested, Cisco Prime would be the best all-around-solution for monitoring Cisco LWAPs connected to Wireless LAN Controllers as you gain much more than just a simple ping alert mechanism. Wireless requires a systemic view that considers not only individual APs going up and down -- and any good wireless deployment has allowances for that to prevent a single AP being so disruptive to the system -- but includes the ability to see AP coverage and overlap as well as interference.
Since wireless is inherently a dynamic system responding to environmental changes -- bodies moving about, different reflections of signals from static objects moved on occasion, and AP power adjustments from detection of surrounding friendly or rogue APs -- you need a platform that deals with all this (as the WLCs do) and a network management system that shows you this system view with the ability to alert when issues arise.