NetSpeedMonitor - NetSpeedMonitor is a lightweight Network Monitoring Toolbar for your Windows Taskbar
MenuBar Stats - Advanced Mac system monitor right from the menu bar
NetTraffic - Essential network bandwidth monitor.
iStat Menus - "An advanced Mac system monitor for your menubar."
FreeMeter - Monitor network bandwidth (C#.NET 2k/XP+). Desktop and Systray graph.
Stats - Simple macOS system monitor in your menu bar.