The problem is that to monitor your sleeping patterns, a valuable feature most of these new smartwatches support, the watch needs to be on your wrist. So leaving your watch charging overnight while you slumber isn’t going to work. But smartwatches have small batteries compared to smartphones, so should only take 2 - 4 hours to fully charge, depending on the model.
Our top pick for most people is the Apple Watch Series 4 with GPS (starting at $399), which has a huge display, ultra-fast processor, Raise to Speak Siri, fall detection and a built-in electrical heart rate sensor for taking on-the-go electrocardiograms. It also runs watchOS 5, which makes the watch even more useful with automatic workout-tracking, offline podcast playback and a Walkie-Talkie voice chat feature.