A network latency monitorhttp://oss.oetiker.ch/smokeping/
SmokePing is a network latency monitor which works in a way that is similar to MRTG. It measures network latency to a configurable set of destinations on the network, and displays its findings in easy-to-read Web pages. SmokePing has special support for monitoring hosts with dynamic IP addresses. SmokePing uses RRDtool as its logging and graphing back-end, making the system very efficient.
The presentation of the data on the Web is done through a CGI which creates graphs on demand.