Your phone might not have great battery life. Many parents who use a wifi baby monitor come to the realization that their smart phone battery life isn't so great when they are streaming a live video and audio feed from their baby monitor. If you have a newer iPhone or Android device, it will probably do pretty well, but if you have an older phone the batter is probably a bit weaker already and you will notice your battery life dropping pretty quickly during use. So definitely consider battery life and charging options for your smart phone when you are choosing between a self-contained versus wifi baby monitor.
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.