Most people don't have unlimited data plans for their smart phone, and are surprised to see very high data usage after just a few hours of streaming their wifi baby monitor. With HD video, you can go through a couple gigabytes of data in just a few hours, so keep that in mind. If your phone is connected to wifi that won't matter, but if you're using 3G or 4G LTE cellular service, you will definitely have slow video and tons of data usage.
If you sleep in the same room as your baby or live in a small enough space that you can always hear or see what your baby is up to, you probably don’t need a monitor. Otherwise, most parents enjoy the convenience a baby monitor provides—instead of needing to stay close to the nursery or constantly checking on your child, you’re free to rest, catch up on Netflix or get things done around the house during naptime. Monitors can also double as a nanny cam to keep an eye on your child and their caretaker.