For all of us who

can touch-type
enjoy the ergonomics of putting the keyboard on the lap
but abhor having the screen only a few cm above the keyboard (like on a laptop)
and prefer sitting in a reclining seat, or sofa, where there is no suitable surface for a regular pointing device

there is now a solution: the trackball lanyard.

Finding that wireless trackball will be as easy as locating your belly button, that is, you will neither have to look, nor reach.

Supplies

wireless trackball
candle + matches + fire-proof surface + fire extinguisher
one stainless steel Sapim bicycle spoke (or equivalent)
some heavy duty string
pocket knife

Step 1: Placing the Holes

The nice thing with trackball pointing devices for the thumb, is that there is a natural, safe place to drill the holes. We do not really expect to find any sensitive electronics in that bridge of plastic which goes around the ball (see picture).

Since I tend to hang some of the weight of my arm on the trackball, and since most of this pressure will be applied by the ball of my thumb, it is a good idea to displace the holes in that direction. If you don't, the trackball chassis will tend to tilt base down, buttons up.

I guess that if you overdo this, the trackball will hang at an odd angle on its own, making it slightly more difficult to grasp it after some busy touch-typing.

Step 2: Drilling

Since these kind of things are usually made out of cheap, brittle, thermoplastics, I find it safest and easiest to drill with a heated bicycle spoke (or, say, a repurposed wire clothes hanger). N.B.: Fire is inherently dangerous. You do this at your own risk.

The holes are made large enough to facilitate the threading of the string.

The edges are trimmed with some suitable tool, e.g. a pocket knife, to prevent them from chafing the string.

Step 3: Adding the String

The string is threaded as shown. If you use two opposed rolling hitches, it will be easy to adjust the length for turbo ergo ninja theoretical physicist working.