Baby monitors are not only for peace of mind but rather a safety feature for your baby twins. You will have many options with baby monitors. Every basic monitor unit has a transmitter and a receiver which you can take with you to different parts of the house. There are also some with a TV monitor so you can view your babies.
AngleCare has a monitor and comes with a board sensor that you place under the matteress and it tracks babies breathing and movements. If after so many seconds there is no movement, it will make a sound to warn you. There are false alarms at times and it can also pick up on other (non baby) movements too. However for premies this is a great tool.
Since I have a tendency to worry, I chose the “FirstSounds Movement Sensor with Sound Monitor by Bebe Sounds” You put a sensor under the mattress which can track the baby’s movement. If after so many seconds the monitor does not pick up any movement it will beep and get you all worked up as you hurry to the crib checking up on the babies and shut it off and on again. Despite having some false alarms, it was worth it for me.