someone asked about the reliability of bike computers above.

I run a bike coop and see dozens of bike computers on incoming donated bikes every year. 100% of them have dead batteries in the head. I remove the computers and install new batteries and resell them for $10. I do remind customers that "there's an app for that". Cateye seems to be the most reliable/durable. Flimsy wires torn off seems to be the main issue on the cheaper/no name brands. Very few are totally dead. I was surprised recently that one newer Specialized Speed Zone Sport wireless model sending unit still had a good battery. That is counter to my experience with the wifes preference for 1990s Specialized Speed Zones that ate expensive batteries, would sometimes reset while riding under high voltage power lines and had false claims about trip distances during her PBP training. This one has a threadless top nut mount so it's a bit newer but it looks like they figured out the battery drain issue on the transmitters.

I have installed many of these on my own bikes for testing. My favorite is a red Schwinn computer on my RWB Schwinn Prelude that records to 0.001 miles. That's less than 1 wheel revolution so it looks like its doing some interpolating. 5280 feet per mile, 5.28 feet or 63 inches per .001 mile. A typical 700 c wheel is 2100cm or about 82 inches circumference.

Another odd one is a Vetta C200 wireless that has an antenna post sticking out the bottom side.

The old Cateye Solar was a dud when new. It used a solar rechargeable button battery that was a failure.

The earliest Avocets were rather buggy and had few features. Auto was not one of them so you had to remember to start/stop it during breaks to get more accurate data. They uses what was basically a cassette tape recorder head and a ring magnet with reversing polarity. The signal was a combo of voltage and frequency instead of the standard on/off from a magnetic reed switch that was used on normal bike computers. I still get a couple Avocets each year but most are trashed.

There are some models that allow you to input actual wheel diameters from 1 to 9999 while others have a range limited to typical bicycle wheels or a preprogramed selection of tire sizes.