I tried one out last year. The video quality was surprisingly good, but there's no audio at all.
I didn't purchase it, and while I was rather impressed by the video for a wireless cam, I didn't see how it was a practical security device so I had it returned.
I spotted a D-Link wireless security cam in some sales circular for around $300, which is pricey but implies it should be a lot more full-featured. I basically decided against DIY home monitoring, but I could be interested if a major vendor rolled out a product line of 802.11b devices. I don't want wireless transmitters interfering with the already crowded 2.4 GHz space.
At the time, Xanboo seemed to be the most ambitious product line, but they are a monthly subscription service and didn't offer any compelling WiFi devices at the time. Haven't really looked into this space since.