I think it would be possible to use a network-enabled webcam as a baby monitor, with the right software. Instead of a devoted audio baby monitor, you'd just buy a webcam, connect it to your home network (wired or wireless), set up some alert software for motion and sound, and you're away. The big advantage here is that you can monitor it from your phone which, if you're like me, you have with you at all times, and it doubles as a nanny-cam too. It also lets you record video of your baby asleep or playing in his or her room and, if you set it up correctly, you could even use it as home security and get alerts while you're away.
I'm trying really hard to think of a down side to this, and the only thing I can come up with is that cameras are creepy. But if you go looking at baby monitors in department stores, I guarantee at least one will have built-in video. So it's not even my idea.
Mokalus of Borg
PS - It might also be less reliable.
PPS - Particularly if it's a cheap webcam on a dodgy network.