The Blaze is a fully featured activity tracker with the accuracy of a dedicated HRM. It counts steps, stairs climbed, calories burned, active time, resting heart rate, sleep stages and quality of sleep, and comes with a number of sports modes that will track particular exercises using its HRM. On top of that, it'll also show you upcoming calendar alerts, texts, and calls.

The Blaze can connect to your phone via Bluetooth 4.0 to send its data to your Fitbit app.

The battery charges up in around an hour, and after that the charge lasts upwards of five days with normal use.

The Blaze was tested against a Quinton Cardiac Q-Stress machine, which is a medical EKG, and was found to vary only by 2-3 BPM at all levels of activity.
You can see the accuracy tests here.