My e bikes give me almost all the info I want except a display of my current heart rate. I have tried my iWatch and a chest strap and iPhone but both run out of battery after about a 2 hour ride. Has anyone found a simple display that talk to a polar chest strap? The only alternative that I have found so far is a bike computer which will also provide a lot of redundant information. All I really want tomsee is my current heart rate at the handlebars!