A couple of friends and I have been chatting a lot about wideband speech coding recently. We have been experimenting with the high-quality modes of the speex codec. I must say 16kHz wideband audio really sounds amazing at data rates of 28kbps. Why do people still put up with crappy narrowband cell phone audio? Ok, so AMR is 12.2kbps but it just sounds so terrible! If I and my friends are in a wifi zone at home or the office why doesn't my phone use high quality audio?
Skype is on the right track here. I absolutely love their new SILK codec. I talked to my dad back home in Europe via Skype SILK and it sounded amazing. The best audio call I ever experienced. I am not sure I'd even call it "telephony".
On iPhone-like smartphones with wifi, asynchronous push notifications, plenty of CPU power and decent microphone/speaker there is no reason not to build a wideband high-quality wireless network.