As with any internet-connected device that watches or listens to your home, it's not out of the ordinary to be somewhat wary of a smart baby monitor. All Internet of Things (IoT) devices are potential soft spots for hackers to monitor you. Anything you network can possibly be compromised, and while you shouldn't be afraid of an epidemic of camera breaches, you should always weigh the convenience of these devices against the risk of someone getting control of the feed.
The features we focused on were those we thought either increased the performance of the monitor or made it more user-friendly for parents and increased the odds of getting good quality sleep. We looked for monitors that have sound activation that keeps the parent unit quiet when the baby isn't crying, so parents can potentially fall asleep faster because they don't have to listen to white noise. Some of the monitors were so loud, even at low volumes, that the white noise might keep light sleeping parents awake; this defeats the purpose of having a video product to begin with. We also liked the models with screens that automatically "wake" and/or go to sleep.