An informative thread indeed. I guess, for now, my best bet is to use an RF ring mouse or mouse pen together with the Twiddler. It'll be tricky to use both devices in one hand, though, and I'd hate to use an RF receiver because I only have the usual micro USB port on my Windows tablet. I hope the right technology comes for the Twiddler to also be a reliable mouse substitute.
In case you're wondering about my use case: I'm a mom who works from home. I have a toddler who'll gladly play with a keyboard and mouse, as well as a newborn whom I breastfeed in a side lying position (i.e. I spend most of my day lying down sideways, switching positions with my newborn a few times through out the day). My work mostly involves creating websites, writing, doing basic design work in GIMP and PowerPoint, and basic video blog editing. I use an HP Stream 7, a Samsung Galaxy Note 3, and a fifth generation iPod Touch.
When working on my Windows tablet, the simplest position is to hold it with one hand while using the other hand for touchscreen input. It comes with a few downsides, though. My shoulders hurt after about an hour of work, typing articles is hellishly slow on the onscreen keyboard, and using a touchscreen for design work is laborious. So far, the Twiddler has solved the first two problems for me, but design work still lags behind because of the 8-way joystick.
To my mind, the ideal setup for me is a monocular HMD (because I need to see my kids) that can display Windows (maybe receive a Miracast stream from a laptop or tablet) or run it, and the Twiddler sporting a mouse-resolution navigation device. Seems like I still need to wait some years before that setup becomes available and affordable.