Stealth, I can see where you are coming from re the monitor. But the whingy, little whispery 'I need you' noises usually mean a baby needs you...and the quicker you respond to THOSE, the less the baby will cry.
Speaking from experience - ds2 cried exactly twice in the first 6 months of his life. Twice. Seriously! And I'm not showing off because truthfully I am a shite parent in lots of ways, especially with ds1! But with ds2 I had learned the sound of 'I need you' and went to him every time, as soon as I could (yes, very little in the way of other demands, which was sheer luck) and it didn't progress into crying.
Just two times, and those were times I carried him around but he couldn't be comforted, which may have been wind or whatever...some kind of distress.
After 6 months, he started getting teeth and it all went tits up but the absolute KEY to it I feel is listening to their little noises, their moans and whispers and grunts, and responding to those as soon as possible.
That is how they learn to wait. Someone will come, they know it. Each time you come before they are desperate, they grow in confidence.
Conversely every time they have these little signals ignored until it becomes a cry, they lessen in confidence, thus crying sooner the next time, in anticipation of being forgottoen/made to wait.
Hope this makes sense. It certainly does to me.