What would be good software for monitoring multiple small and disparate networks?
My company sells a product that requires deployment of a number of Linux servers on a customer's network (typically three servers but may be more). We currently have such deployments in 25+ networks and this number is growing. We would like to monitor the general health of the machines as well as the status of various custom bits of processing on each of these networks. We connect to them in a variety of ways (direct SSH, VPN, WebEx, etc) and so being able to see everything from both the command line and a web interface would be useful.
This information would be aggregated (somehow) at our office for an overview, but that mechanism is beyond the scope of this question.
I am aware of "What tool do you use to monitor your servers?" but that seems to cover monitoring the entire network as well as large networks. Some of these seem too complex for monitoring just a handful of machines per network.
I have been experimenting with Nagios but would like to know if there were more suitable tools for our particular use case.