Hey! Check out these these eco drive watches! They are powered by light - any light, not just the sun - so that makes them... is that still solar-powered? (I don't know much about Geology.) Anywho, they are really nice watches that never need a battery, so not only are they eco-friendly and good for the environment, they save you money. And watch batteries can be rather expensive, depending on the type your watch needs - I am guessing the more expensive the watch, the more expensive the battery, but that is just a guess.
While it is true that all these techno-gadgets with which we are surrounded these days all have clocks, I love wearing a watch. And, more than once, I have actually needed one! So check them out and feel good that you are doing the world a favor.