IME, the only reliable heart rate monitors are those with a chest strap. I've always been happy with Polar products. On the bike, one affixes the watch to the bars using pipe insulation or the manufacturer's bracket, where it is easily visible. A simple monitor, just displaying HR, is not expensive. I used one for many years before I decided I would like to upload my data, which involves a considerably higher price point. Such watches usually have a GPS function which also records route and distance. I now use a watch device for gym, running, and walking or hiking, and a Garmin cycling-specific device for the bike, which has a much greater battery capacity as well as a larger screen with more information.
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