I posted the code here. I think the firmware is done, and I've finished the Vim plugin.
I'll try recording some videos of this thing in action on the weekend.
I really wanted Normal mode in Vim to map to Neutral on the shifter, but the shifter physically won't let you move it to the "M/S" gear shifter side unless it's in Drive mode. So currently Drive is mapped to Normal, and Neutral is mapped to Insert mode.
I also made it so that when you tab out of Vim, it puts the handle in a "general" mode where moving the handle will cmd-tab between apps, and also page up and page down. You can see the key mappings here