I followed the news about the sansa connect with high interest and I am really hoping you make it! Its a great toy!
One detail in the hardware description that I wonder about is the VOIP-Chip that is listet here:
http://www.rockbox.org/twiki/bin/view/Main/SansaConnectDoes the sansa connect have a microphone? or could you use a headset with it (theoretically) through the headphone jack?