I currently use two watches, one automatic mechanical watch that always has enough energy in its spring, as long as I use it during the week, and one cheap smartwatch that cannot last much more than a day.
I like both and wondered whether arm movements provide enough energy after conversion to run a smartwatch with basic features, such as Bluetooth music, GPS tracking, heart rate sensor, and vectorial maps...
That would be a smartwatch that doesn't have to be charged ever and have cool mechanical engineering too.