Web cams rock. You can set up some simple security in your house with software like Home Watcher or just take periodic simple snap shots using Cam Commander. You can also video chat using Yahoo Messenger or Microsoft Messenger.
If you have a permanent broadband connection, like cable or ADSL, then it isn't too hard to have your web cam up and going all day.
You will, of course, need a web cam. You should be careful because they are not all the same. There are some cheapo CMOS web cams out there that produce low res blurred images. There are some really nice cheap CCD web cams that produce images that are very sharp. A good idea is to get a web cam with a built in microphone, as they are generally good quality for chatting, although headphones with the pull down microphone seem to be taking over the world. I have never really had good luck with microphones as all the cheapo ones seem to be way too quiet / muffled no matter how I fiddle with drivers and filters.
If you have a bit of money to spend you can go hunting for network cameras. The good ones plug into your network and act as a web server or can be configured to upload images / video to a specified site. Wireless wifi cameras are also becoming more readily available - just set up your wireless network, configure the camera and place it where ever you wish.
Recently there have been google searches noted that allow you to find open cameras that you can freely access. Most of these are public places and offer an excellent way to view the world. To see live snow falling over a telescope dome in a forest while I am sitting here in sweltering weather is quite thrilling.
Amusing for a while anyway.
Yes there are many "Adult" sites that espouse web cam, but just avoid that stuff, they will ask you to download and run their virus ridden software that will fill your computer with advertisements. I have had to rescue way too many people from this sort of software. The dubious sites always seem to request your credit card details as verification - never ever give your details away unless you are absolutely certain that the company is legitimate and that the web site you are on is the exact web site of the company. There are so many web sites pretending to be a bank, or pay pal etc that you REALLY have to be careful.