While my original idea in making up the bike electro-mechanic odometer described in the last past was to get rid of batteries on a bike, a friend told me that for ordinary people getting rid of the spoke sensor of the classical odometer is a much better selling point for the hub-dynamo driven odometer. Batteries in bike odometers usually last several years, so there is little pragmatic need to rid of them. I also agree with him that most people will probably prefer a digital odometer (much resembling the ones on the market now) to a mechanical one. While I still think that an electro-mechanic odometer would be a nice luxury bike component (just like Swiss mechanical watches are still a popular accessory among the rich elite), a more traditional digital odometer would be much easier (and cheaper) to make and could offer the features at the same price as state-of-the-art current odometer – just that it dispenses with the spoke-sensor and batteries.
My friend and I have come up with two ways to make a sensor-less and battery-less odometer: first is to use off-the-shelf generic components like a dot-matrix LCD and micro-controller – this allows us to build an experimental prototype at low cost as well as some practical devices for our own bike at an affordable price. We agreed to build this together just for fun!
If we ever were to commercialize it, however, we would need to drop to price to the same €20 range as current commercial models which requires custom-made components that are mass-produced with high initial investment cost. Personally I think there could be a middle way by re-using the shell and LCD of a cheap generic odometer and just replace the electronics with ours. In Europe (at least Denmark, Netherlands, Germany, Austria, and Switzerland) hub dynamos are now common place on utilitarian and travel bicycles and even on some sport bicycles. (That's because dynamo-lights are legally mandated for bikes used in public traffic and hub dynamos have replaced all other dynamos on new bikes.) Therefore the market for a spoke-sensor-free and battery-free bike odometer is huge. There are currently ca. 5 million new bikes sold in Germany each year and the amount is probably the same in the sum of the other four countries mentioned. If half of those bikes has a hub dynamo then that's 5 million potential odometer-buyers each year just in those five countries!