I just purchased a tented split keyboard to alleviate some of the repetitive stress on my hands from typing, which I use with my MacBook Pro. It's working great overall, but I'm annoyed by the need to move my right hand off of the keyboard in order to scroll.
Using PgUp/PgDown or Space/Shift-Space is insufficient for my needs, because I've become accustomed to analog control of scrolling, and the visual jump of scrolling a whole page -- not to mention losing sight of the last thing I was looking at, or even jumping past a bit of content (very common on websites with a fixed top navigation) -- is too disorienting.
To solve this, I would love to have a small analog pointing device, i.e. a scroll wheel or joystick or trackpoint or trackpad, that I could clip onto the side of my keyboard and manipulate with my index finger or thumb. It would have to have its own Bluetooth support or at least be easy to use with a USB-to-Bluetooth adapter.
I don't necessarily need the device to be ready-to-clip, as mounting could be jerry-rigged with binder clips or solved with a custom 3D printed part.
If there's anything that occurs to you that would fulfill my need but doesn't conform to the description above, I'd love to hear about it. (Perhaps I will have to take apart a cheap Bluetooth mouse and just keep the scroll wheel and PCB.)