App request: record & external speaker from headphone input

[porsche996]

I asked a question similiar for the OG Droid a while back, and just realized the answers I got before aren't necessarily true.

So, here goes again...

First, I know you can use a wired headset for voice calling; all cell phones can do that for years. Realizing that, the headphones jack goes both ways, output AND input...

So... Has anybody ever seen an app that could make use of this, and turn the phone into an external speaker for an audio supply? I don't see why this wouldn't be possible since the hardware for allowing sound input is in there (this is where I realized the OG thread I started on this isn't true), and if you can talk into the phone for phone calls, surely there's a way to do this...

Basically, my wife is pregnant, we have a heart beat monitor, and it'd be really cool to be able to use the phone as an external speaker and/or recording device!

[jmichaelm]

There will be impedance and level matching issues connecting an output meant for a speaker to an input meant for a microphone. I doubt this could work unless you use something like a DI box to connect them.