Under 11.04, the option to control the pointer with the numpad was set in Hardware/Keyboard settings page. How can I turn on mousekeys or configure them in 11.10 or later?
I'm interested in both Unity and Unity-2D.
In 11.10 and above you go to System Settings in the Power cog menu and select Universal Access.
Under the Pointing and clicking tab you will see a slider that lets you turn Mouse Keys on and off. The label says: Control the pointer using the keypad.
In addition to grahammechical's great answer, I thought I'd add a couple of notes.
This procedure is the same in 12.04 as 11.10, and it is nicely documented on help.ubuntu.com . Because those instructions have been kept up to date, it's likely that the documentation will also be extremely helpful for future versions of Ubuntu.
Here are the links for mousekeys in versions 11.04 through 12.04 -- note that the url is identical with the exception of the version number:
Because 'mouse keys' is considered an accessibility option, I thought I would repeat the textual instructions from the 12.04 version of the help site. The instructions are screen-readable or suitable for low-vision users, though the procedure is actually the same as the "power cog"-based version from grahammechanical.
Nevertheless, for 12.04, the configuration there is given as:
For Unity, it seems easier to hit the Super, type in the first few letters of "universal", then skip to the third step given above ("Select the Pointing and Clicking tab".