Calling all parents! How are you able to hear your kids if they wake up?

I play with headphones to not wake anyone up, and I like to get really immersed with loud volume. My son (soon 2 yrs old) wakes up once in a while, and it would be so great if there was a way to hear him - maybe have my phone propped up in his room and have a skypecall going to the ps4. Unfortunately, Skype isnt available for Playstation (?).

Any suggestions? How do you peeps do it?

Thanks!