I used to have a cheapish computers for each of my bikes that stayed on that bike, but now I have a single Garmin that I switch between all of my bikes (road, mtn, cx/commuter).

Between forgetting to switch between profiles when changing bikes, and forgetting to press "Start" at the beginning of every ride (who thinks to do that on commutes?), I no longer have any idea what my "real" odometer reading should be for any bike.

I used to use this data to keep track of how much I ride each bike, how many miles various components had on them, and as a matter of pride. My co-worker and I used to go for bragging rights for yearly/monthly mileages. Now I have no idea what any of that data is.

What I'd like is to have a simple odometer for each bike. It doesn't need to do anything at all other than keep track of miles or even just wheel rotations - I can do the math later. I don't need speed, avg, cadence or any of that stuff. It doesn't need to be wireless or anything fancy. I'll probably mount it somewhere out of the way, like at the bottom of the seat-tube near the bb. Small size, weatherproof and relatively cheap would be good.

Does anything like this exist?

Even the cheapest come w/ nine or ten functions. I just ordered a couple of these (Bell F12), at less than $10 apiece, for my wife and daughter.

I used a CatEye Enduro 8 (https://www.rei.com/product/696924) for the past 4 years. I replaced it recently not because it died, but because I wanted GPS tracking (Garmin Edge 500). I've thought about mounting it somewhere unobtrusive (e.g. on the seat tube) just to have a constantly running bike odometer regardless of what other gadget I'm using that day.

The Enduro 8 can't match the Bell F12's price (about $30 vs $10) but it was a durable little computer.

$6.46 shipped. Note that this will take 3 or 4 weeks to arrive.

https://www.dealextreme.com/details.dx/sku.32804

They have a few other models but this is the cheapest one and gets OK ratings.

There used to be mechanical odometers that attached to your front wheel axle, and worked like the odometer on your car. A peg which attached to one spoke, turned it slightly each time the wheel turned.
Haven't seen one in a very long time, though

If you set up the display to show "Grade", you will have a reminder.
The grade displays as "__" if you have not pressed "Start".

I have it set up that way already and I still forget. I suppose I'll just find the cheapest computer I can find -- I was just hoping for something super small that wasn't very noticeable.

You know what would be cool is if the Garmin speed/cadence sensor had a counter built into it and that number was simply sent to the GPS to be displayed in the odometer count. That way the number would stay with the bike.

You could get the cheapest computer and mount it someplace non-traditional, such as inside a frame bag or under the top bar...

I just bought one of these. Less than $6, and free shipping.

The seller is in Hong Kong, so the shipping took two weeks.

I installed it on a customer's bike. It works! It even has a thermometer. I'm very satisfied with the product and the seller. They have a weird mixture of products and excellent prices. I had occasion to use their customer support, and the people were polite and helpful.

https://www.suntekstore.com/cycle-bik...-__-black.html

How water-resistant do you think it is? Whatever I get, I plan on mounting it near the bottom bracket.

Wal-Mart and Target have cheap, functional computers.

that looks like the schwinn computers that are available at Wal-mart and the like, for a bit more (but no shipping delay.). The heads are completely water proof. The contacts between the holder and head is the only thing that's subject to water problems, but they work in everything short of blinding downpours. a little dielectric grease probably would solve that, too.

Amazon has the Schwinn computers, too. I hear the bracket can let the computer fall out, though. I haven't tried it myself, though. I have one still sealed in its package.

I don't know how waterproof the no-name unit is.

The patent on the chip behind these must have worn out. Anyone can make a bike computer nowadays. That's why you can get them so cheap. I don't know why I'd pay more than $15 for a basic computer. At my LBS, they are $40, minimum.