Re: Speedos

> Obviously it doesn't make a permanent record...
Not sure what you mean here. My bicycle speedometers have registers for total accumulated mileage as well as trip mileage. The unit on my mountain bike even tells me how much time I spent actually moving (i.e. A trip may have lasted 3 hours, but the bike was only moving for 2 1/2). They keep the total mileage until they are reset, the battery is removed, or goes dead.
I've also found them to be quite accurate if I follow the custom calibration procedure instead of relying on a value from a look up table.