I used a baby monitor when all my children were babies.
One, it offered me peace of mind when I was asleep that I'd hear them if they were crying and needed me - if I'm r e a l l y tired I can sleep like the dead - and two, it allowed me to move around the house and garden whilst they were snoozing during the day and, again, hear them when they woke up.
This Fisher Price Musical and Digital baby monitor plays three lullabies and nature sounds, it also has a night light.
All of these things can be activated by remote control via the parent unit so you don't have to go into your child's room to switch them on; it can be fatal if they see you..."OOOH look! Mum/Dad have come to see me, it must be time to get up and a) play or b) have cuddles for hours and hours and hours!"
The Fisher Price Musical and Digital baby monitor is an Argos online exclusive so you can't order it in-store. You CAN arrange for it to be dropped off at a store for you to collect though, or you can arrange for delivery to your front door for £5.95.
Thanks to Haylhoo at HUKD