From a pure imaging standpoint, night vision is vital for watching your baby sleep from another room, and is standard for most baby monitors. Motorized pan and tilt (which lets you swivel the camera from afar) isn't quite as common, but is very welcome if you have a toddler and want to scan an entire room. High-definition is a nice plus, but you don't need the highest-resolution sensor to keep tabs on your baby—most of the monitors we test use 720p cameras rather than 1080p.
A word of caution about extremely cheap baby video monitors (we're talking devices that cost less than $50): they're not known for their security and can be hacked. Be sure to always change the default password of any connected device you purchase. You can also protect yourself by sticking to known vendors who post frequent firmware updates and have easy-to-reach customer support.
Wireless encryption: This ensures that no one else can tap into your monitor’s “feed” and see what’s going on in your house. WiFi-enabled monitors are great for portability and range, but may be more susceptible to hacking. If you go this route, be sure to secure your home wireless network and keep the monitor’s firmware updated. Otherwise look for digital monitors with a 2.4 GHz FHSS wireless transmission.