Bashtop is described as 'Linux/OSX/FreeBSD resource monitor' and is a Process Management Tool in the OS & Utilities category. There are more than 10 alternatives to Bashtop for a variety of platforms, including Linux, Mac, BSD, Windows and iPhone. Most alternatives are Process Management and Process Monitoring Tools. The best alternative is htop, which is both free and Open Source. Other great apps like Bashtop are Glances (Free, Open Source), KSysGuard (Free, Open Source), BPYTOP (Free, Open Source) and GNOME System Monitor (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.
KSysGuard, also known as KDE System Guard and KDE System Monitor, is designed to make simple process control available to a user without needing to do any special setup - the defaults are usually perfectly adequate.