cPingProbe is a multiplatform (Windows, Linux, mac OS, Solaris) multi host pinging tool that would continuously record your RTT from pinging machine and would notify on any discrepancy from normal trend. Its a great resource friendly tool that would do it task without starving other application of system resources.  Currently it supports 3 protocol methods to test host round trip time. TCP(default) , ICMP(standard) and UDP(generally not recommended for long term analysis).