SmokePing

SmokePing is a network latency monitor that continuously probes hosts and services and draws them as graphs, so you can see not just whether a link is up but how much jitter and packet loss it carries over days and weeks. It tracks latency distributions, packet loss, and history per target, supports many probe types including DNS, HTTP, and external bandwidth checks, and can raise alerts by email or by running a script.

Network administrators use it to spot degrading links before users complain.

Running it on your own installation keeps probe targets and topology private, has no per-target fee, and leaves a small directory of probe data that is trivial to archive.