Environmental sensors: Many monitors include the ability to set thresholds and upper limits for room temperature and/or humidity, and they'll alert you when these ranges are exceeded. While they can't control the temperature or the amount of moisture in the room's air, this feature can help you improve your child’s comfort, which will help them get more restful sleep.
Range of signal: Some baby monitors have better range than others. If you live in a big house with multiple rooms, range will be a key consideration for you. Anyone who lives in a single-story house or a smaller apartment may not need as much range. Many baby monitors have an alert when you get out of range, and the packaging typically gives you an estimate of the range. Bear in mind that range varies widely from home to home. The construction of the walls between you and the baby monitor may even limit the range.
Before buying or registering for a baby monitor (or any wireless product), be sure you can return or exchange it in case you can't get rid of interference or other problems. If you receive a monitor as a baby-shower gift and know where it was purchased, try it before the retailer's return period ends. Return policies are often explained on store receipts, on signs near registers, or on the merchant's website. But if the return clock has run out, don't feel defeated. Persistence and politeness will often get you an exception to the policy. Keep the receipt and the original packaging.
Microphone sensitivity: There’s a difference between hearing your baby cry, and hearing every little noise. All baby monitors have the option to turn down the volume, but some offer thresholds for parents who are more comfortable with only hearing the biggest upsets, and prefer not to hear the self-comforting noises their baby makes as they fall asleep.
The most troubling pattern you see in the one-star Amazon reviews is the reports of battery life declining (or failing) over time. This is part of a larger trend in baby monitors in general, and our take on it is that the battery tech within these monitors is just not at the level people have come to expect after living with good phones and tablets, and other quality electronics. Reading the negative reviews on this and many other monitors reminded us of the kinds of problems people had with rechargeable batteries years ago. Here’s a good example of what we mean. So for now, for any baby monitor, set your expectations accordingly.