What are some alternatives?
When comparing Site Down and NetWorx, you can also consider the following products
Ruler - It's a screen ruler for Windows.
NetSpeedMonitor - NetSpeedMonitor is a lightweight Network Monitoring Toolbar for your Windows Taskbar
IsItDown RightNow - "Is It Down Right Now" monitors the status of your favorite web sites and checks whether they are down or not.
GlassWire - Visualize network activity in detail, get notified when new apps access the network, look out for...
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
DU Meter - DU Meter is a network bandwidth monitor for your computer.