Iotop is described as 'Linux has always been able to show how much I/O was going on (the bi and bo columns of the vmstat 1 command)'. There are six alternatives to Iotop for a variety of platforms, including Mac, Linux, Windows, BSD and iPad. The best alternative is htop, which is both free and Open Source. Other great apps like Iotop are Glances (Free, Open Source), Resource Monitor (Free), Sternum (Free) and Atop (Free, Open Source).
Glances is a cross-platform monitoring tool which aims to present a large amount of monitoring information through a curses or Web based interface. The information dynamically adapts depending on the size of the user interface.
Resource Monitor is a system application in Microsoft Windows operating systems. It is used to view information about the use of hardware (CPU, memory, disk, and network) and software (file handles and modules) resources in real time.
Sternum seamlessly embeds security into your embedded devices. With a new approach to IoT security, Sternum has built a holistic, highly scalable IoT endpoint security solution, that prevents attacks in real-time and provides on-going visibility and monitoring into the device.