Some of his videos I linked to above might show some early prototypes.
Looks like using the key itself as a joystick is mentioned in this patent:
http://www.google.com/patents/US5521596
>The above objects are attained by providing a generally rectangular shaped sensor assembly, including a plurality of sensors, which may be placed either directly underneath an existing key of a data entry device or in between two keys of a data entry device. When the sensor assembly is placed underneath an existing key, the key is used as the analog pointing device. When the sensor assembly is placed in between two keys, a separate joystick is used as the analog pointing device.
Here's a paper that Barrett, Selker, Rutledge and Olyha wrote about "Negative Inertia": using a dynamic force => velocity transfer function to make the trackpoint seem snappier: smoother yet less sluggish.
Negative Inertia: A Dynamic Pointing Function
R. C. Barrett, E. J. Selker, J. D. Rutledge, R. S. Olyha, IBM Almaden Research Center.
http://www.sigchi.org/chi95/proceedings/shortppr/rcb_bdy.htm
>In-keyboard isometric joysticks can give better performance than mice for mixed typing/pointing tasks. The continuing challenge is to improve such devices to the point that they are preferable even for pure pointing tasks. Previous work has improved joystick performance by considering user perception and motor skills. This paper considers the dynamics of the pointing operation. A dynamic transfer function for an isometric joystick is described which amplifies changes in the applied force to increase responsiveness without loss of control. User tests show a 7.8 +/- 3.5% performance improvement over a standard non-dynamic joystick. This feature has been incorporated into the TrackPoint III from IBM.
>[...] Figure 1 [gif file missing] illustrates the effect of the negative inertia filter. The user applies an increasing force to begin a motion, holds constant while cruising, and then reduces the force to stop. The filter causes the motion to start and stop more rapidly while not changing the cruising rate. The velocity may actually become negative at the end of the motion causing the cursor to "back up" slightly. This response causes the cursor to be more responsive without loss of control.
And this parent describes the Trackpoints special force => velocity transfer function:
Method of controlling the velocity of a cursor of a video screen
US 5764219 A
>Input force applied on a pointing device (51) having outputs (x,y) is related to the velocity of a cursor on a video screen according to a transfer function (FIG. 2) substantially described by a parabolic sigmoid function, thus resulting in adapting the force/velocity relationship to accommodate human perception and motor control limitations and task specific coordination problems.
https://www.google.com/patents/US5764219?dq=ininventor:%22Ed...
I hear the new square Blackberry has the keyboard itself double as the touch sensitive trackpad. I haven't tried it, but that instantly sounds nice - like the inverse of a touchscreen keyboard, if you will.
Do any of you know of a desktop or laptop keyboard where the keys - F and J particularly - work as trackpads?