I backed the crowdfunding campaign for these many years ago. The HR tracking is surprisingly accurate and updates quickly. Obviously there are a load of smartwatches and fitness bands out there that also track your heart rate, which makes this look like less of a bargain.
That said, if you want to track your heart rate, and you don’t have a device that already does it, and you don’t want to spend the money on a “smart” device that will be obsolete and unsupported in a year or two, this is a pretty good buy. I wear an Apple Watch these days, but I still keep my Mio ALPHA around as a back up. I expect that I’ll still have it as a back up many years from now.