Sound devices relay what is happening in baby's room via sound only. A great sound option is quiet unless the baby is making noise so that you won't be disturbed by white noise or constant static. This basic monitoring type can be all you need if your goal is being alerted when your baby is crying and needs your assistance. This style can be elementary with sound only like the V-Tech DM111 or it can have bells and whistles like a nightlight, 2-way talk, lullabies, and mic sensitivity adjustment features like the Philips Avent DECT SCD570/10. Most parents can get by with a sound only device as it provides the information you need to determine if your baby needs you or not.
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.