New Delhi, Sept. 14 -- I started looking at smartwatches for a fairly simple reason: I wanted something I could wear overnight and use to understand my sleep better. That quickly turned into a much longer checklist. I wanted useful sleep-stage information, reliable health tracking, a comfortable design and enough battery life that I would not have to remove the watch every night to charge it. The five watches here take very different approaches. Samsung and OnePlus focus on full smartwatch features, Fitbit leans heavily into wellness tracking, Polar is built around training and recovery, while CMF offers a more affordable everyday option. I have also looked at what Amazon buyers are saying, because battery life, accuracy and reliability c...