I recently met with Netcordia and learned about their VoIP Analysis Module that works with their NetMRI product. The product does active testing, QOS analysis and can make a path diagnostic chart showing you where the problem areas are. It can tell you if QoS policies are not enabled for example.
It can tell you about jitter, packet loss and other variables you need to know when managing VoIP in your network. The program uses SNMP to capture MIB data from devices across call paths.
The cost for the product is $25k for 200 routers and switches and 5,000 interfaces
QoS and monitoring ar hot areas in VoIP now. I don't see this area slowing down as voice quality will be a concern for quite a while.