Flemming's electric glider now has an on-board variometer. Well, more than just a variometer. It's combined with a GPS device. It measures, records and transmits not only the rise and fall of the aircraft but also speed, height, location -- the Full Monty.
The feedback to the pilot is by a rising and falling tone punctuated every now and then by a businesslike female voice giving height above ground.
The tube attached to the fin is a Total Energy Sensor. This allows the device to integrate the kinetic and potential energy of the aircraft. In theory, if the aircraft loops, exchanging speed with height around the loop, the device will give out a constant tone. And so it does. I've seen it with my own eyes, and heard it with my own ears.