I had a club-mate years ago who made a monitor mount for his handlebars from one of those oval forms that watches come mounted on, when they're still in the manufacturer's packaging. He had a reputation for being a bit of a cheapskate, but that particular innovation was kind of clever. Last winter I mounted my Polar on my handlebars by winding an old sock around the bar and strapping the Polar watch to it. A necklace wouldn't work for the model that I have because holding it next to the chest strap changes the mode.