I am glad that this app exists. It is really useful already.
But also, it is still very young. I think it could be improved in many ways, e.g.

• make the parent number selectable from the contacts database
• put the sliders for threshold on the main window so the user can see the effect of a changed value immediately
• even better: move the audio slider directly into the live audio graph as a movable ruler line
• on program startup time, set the values to an auto-adjusted value, depending on noise in the environment

I hope the Babyphone app will be actively improved...
and a big THANK YOU for providing this useful app for the N900!