iotop does for I/O usage what top(1) does for CPU usage. It watches I/Ousage information output by the Linux kernel and displays a table of current I/O usage by processes on the system. It is handy for answering the question "Why is the disk churning so much?".

Package page: http://maemo.org/packages/view/iotop/
This is actually latest iotop (official site), with some UI modifications to make it more usable on small screen. The process name was moved to the left part of UI and if you increase the terminal size, it will drop some additional information out, but keep name and basic IO info.

See more on screenshots:
Optimized interface:


Minimum font size:


Maximum font size:


Only active processes mode (toggle by pressing 'O'):


Please, refer to official iotop documentation for usage help.
Install:
Package is in extras-devel yet.
Note, it's written in python. It will be installed automatically if not installed.