I have been a fitness freak myself and I love experimenting with gadgets. I purchased this band about an year ago and love the same. It tracks your calories burned when you are active, tracks steps taken and distance travelled the decent aspect of it that even if you are moving with your hands in your pocket, the sensor still detects your movement. This is one of the cheapest band. Furthermore it also tracks the efficacy of your sleep.
However it does not yield few important aspects like resting metabolism and heart rate which is imperative for fat burn.
Having said if you sync the application with Google Fit it even gives you calories burned during rest.
My suggestion would be a good start if your aim is to improve health but If your aim is higher like six packs or a ripped musculature you might have to look for advance trackers as it does gives great amount of data.