I think it was shortly after the first time I had taken apart a computer mouse that I had this idea. I must have been about 13 years old, or somewhere around that. For some reason this is one of those project ideas that I can't forget about. I usually don't pick up on these ideas. But other ideas don't pop back in front of other project ideas ever other year. And this one isn't even one that would be useful to me or anybody I know. Maybe I can get closure by posting the idea here.
So, you know how ball mice worked? The ball would rotate two separate wheels (one horizontal, one vertical) when the mouse is moved. So there are sensors that pick up horizontal and vertical movement independently. One could attach the drum/wheel to anything else that can be rotated. So one could, for example, connect one of the wheels to a crank, or a rollerblade wheel, or whatever. So then, instead of a small plastic mouse on the table, you could handle a different object, that suits you better. Specifically, my idea was to connect both wheels to wooden foot rollers. So one could move the right foot up and down to move the mouse pointer vertically and the left foot to move it horizontally. pressing down on each roller would produce a left or right mouse click respecively. The intention, besides having a cool new way of sending input to a compuer while sitting at a desk, was to remove the possibility to move a hand from the keyboard to the mouse and back. But I suppose it could possibly also be useful to people who don't have hands or can't manipulate a regular computer mouse with one of them comfortably.
I even got myself a pair of these foot rollers. I have enough cheap ball mice to sacrifice one or two to such a project. But here's the two problems, who's combined result is that I never started to build even a proof-of-concept prototype: It wouldn't be incredibly simple to create (orientation of the rollers, reliable connection to the sendors, additional complications for scrolling wheel) and I don't actually need a device like that. I don't have to switch to the mouse that often if I know the software that I'm using well and/or have it configured to my liking. Maybe it would be cool to train using this device so much that I could use it effortlessly and navigate a GUI fast with it, maybe even to be able to use it for graphics work. But what then? Even if I'd use it enough for it to become actually practically usable by me, I would at the absolute best end up where I've started: Using a convenient graphical input device, only this would would be less portable and I would expect one to be available at any desktop computer. It would just complicate things more than it could help make things easier for me.
So, here, take these pictures of the components that I could but won't use to build a mouse alternative and, well, probably forget about them immediately.