Here's a fun one that brings electronics tinkering, 3D printing, and spirited driving all together in one place!
An engineer at Ford has hacked together a stick-shaker that can communicate optimal shifting points to the driver. A similar concept exists in commercial aviation cockpits -- the flight stick shakes when the plane is operating at its limits.
This shifter certainly would have come in handy when I first learned how to drive stick, and when I later progressed to (ahem) spirited driving.