Glad to see someone's already covered Fingerworks. I'm still sore at Apple, though, for shutting them down and sitting on so much of their gestural vocabulary. My TouchStream keyboard let my wrist RSI heal, and I still miss it (it eventually failed after a number of years). If I could buy another, with support, I'd do it in a heartbeat.
I see a lot of people here complaining that "trackpads suck" and "gestures suck" and "tapping sucks", because (apparently) their trackpads suck. I'm totally happy with my Macbook Pro's trackpad, with one push-to-click surface, which I only use for dragging; taps for everything else. But, yes, using the trackpad on an HP laptop was physically painful.
Fingerworks did a remarkable job of getting gestural and zero-force input right. Apple didn't completely ruin it when they bought out the technology. It would take a lot to independently engineer a system that works as well, but if anybody has the resources to do it, it's probably Microsoft.