I had a cool idea the other night. My wife and I have been in hotels with the kids before, feeling trapped in the room once they’ve gone to bed. You’re stuck because you can’t leave them unmonitored, and you can’t make noise inside the room, because you’re in close quarters with a bunch of sleeping kids. Regular baby monitors are unlikely to have the range required to monitor your kiddies while you’re in the lounge down the hall. So what’s the answer? Turn your laptop into a streaming internet radio server and tune in with your iPhone.

I’ll describe how I put it together with the hardware and software I already owned, and you can probably modify the set-up to your own needs. On the laptop side, I used my 17″ MacBook Pro running the superb $40 Nicecast from Rogue Amoeba.  Nicecast takes an audio source of your choice, such as your laptop’s internal microphone, or an application such as iTunes, and will serve a live radio stream of that audio source. (Nicecast will also relay the audio to a dedicated streaming audio service such as Live365. I’m assuming that if you have or are willing to pay $10 a month for such an account, you probably know how to do this already.) Because we’re not looking for high fidelity here, dialing the bitrate down to 24Kbps on Nicecast’s “Quality” tab will conserve some bandwidth, making the stream more palatable for use over AT&T’s data network. It won’t kill you to conserve CPU as well.

Nicecast Quality tab

Pick “Audio Device” from the “Source” menu, 

Nicecast Source tab

mute the volume (laptop feedback won’t help a sleeping baby!), and click “Start Broadcast”. The on-air level monitor should be responsive to room sounds.

Nicecast main window

On the receiver side, I use my 3G iPhone and the app Tuner by Nullriver. Tuner can listen to a streamed mp3 source such as the one generated by Nicecast. In Tuner, tap the “Search” tab, then the “Open” button.

Tuner Open Stream pane

That’s where you’ll be able to enter the URL of the Nicecast stream (or technically a playlist file referencing the stream), which Nicecast helpfully provides on its “Share” tab.

Nicecast Share tab

Now under some circumstances, that might be all it takes to start listening to your laptop’s mic from anyplace in the world you can get a data connection on your iPhone. In particular, if your laptop is behind a router that provides UPnP or NAT-PMP, Nicecast will automatically configure it so that your stream will be exposed to the internet at the URL listed under “Internet” on the Share tab. But this is not likely to be the case if you’re on the road, using commercially provided internet access. Part 2 will discuss how to overcome this limitation.