if you have a spare computer and webcam, then you can use something like yawcam for windows to make it stream over your network, and with some additional setup - over the internet.
720p webcams like the Logitech 9000 or Microsoft 5000 see things in lower light conditions that the older vga sensors / cameras can't even pick up.
If you don't mind setting up the spare computer with linux, then you'll have more options to set up streaming audio and you can really into it as detailed here.
yeah I was looking at things like the foscam. we actually have a baby monitor, but we're also having a new baby so we're going to need a secondary device.
I have one of these from the first baby: Philips Avent DECT Baby Monitor w/ 2 Parent Units SCD590/54DAKmart
it's great, except the recharging bases are just really really stupid and they always charge the batteries even when full, so the rechargeables just don't last.
I was hoping to find something that would just plug in to the network, and then try to work out something for the parent unit
I was looking at the 3-packs of the foxcam.
Amazon.com: 3 PACK Foscam FI8910W Wireless/Wired Pan & Tilt IP/Network Camera with IR-Cut Filter for True Color Images - 8 Meter Night Vision and 3.6mm Lens (67° Viewing Angle) - Black NEWEST MODEL: Camera & Photo
one for each kid's room and then one to play with. the thing that makes me a little hesitant about it is that they are a little overkill for what I need and a real parent unit just doesn't exist.
this seems intersting: Amazon.com: Uniden UDW10003 Wireless Video Surveillance Portable Security System: Camera & Photo
but it doesn't look like it's a standalone IP cam.
Monoprice has some good cheap ones but you would need to run audio separate.