RAX120 - is there a software tool to watch the speed out of the router continuously?

Tests like that are more tricky. For general tests, you could repeatedly run a speedtest.net test, but if you want a constant transfer, then the most reliable way to do it, is to have your own VPS that has a dedicated connection above 1Gbps ( or at least twice the speed of both your home WAN connection's upload and download speed, and then have it act as a iperf server. While more expensive, it is a more reliable way to measure a single connection's throughput over a more extended period of time without being influenced by other people using the same server to test throughput.

Though often a more common method of longer term test is running 3-4 speed tests in a row every hour throughout a day in order to keep track of how your WAN throughput changes over the course of a day. This is especially more useful for people on cable internet connection since the shared throughput nature has a higher degree of variability in the speed, and knowing it will impact how you go about implementing QOS, and various other functions.