HRM-Dual is the latest Garmin heart rate strap in their line up. Unlike previous models, the new HRM-Dual can connected via Bluetooth too. All the previous models relied solely on ANT+, which was fine. Garmin watches are using ANT+, so the HR straps use using ANT+. But the market is changing with new products like indoor bike trainers (Zwift) and smartphone apps. Some competitors of Garmin have been offering Dual connectivity HR straps for a long time.
The price of the new HRM-Dual is $69, EUR 69. Official description from Garmin:
This premium heart rate strap transmits real-time heart rate data over ANT+® connectivity and BLUETOOTH® Low Energy technology, giving you more options to train indoors, outdoors or even online. With it, you’ll be able to consistently receive accurate heart rate on your Garmin device, in online training apps such as Zwift or even the compatible fitness equipment in your favorite class at the gym. So however you like to train, you’ll get the accurate, real-time heart rate you need to take your performance to the next level.
HRM-Dual features a soft strap that is comfortable and adjustable. Simply remove the heart rate module, and it’s washable, too. And don’t worry about running out of juice. The battery lasts for up to 3.5 years.