We have a "cat cam" set up. We have a Panasonic BL-C10 network camera (so no PC required). It's a lower-end model (wired rather than wireless, pan and tilt but no zoom, live video only, no recording) but works well for our purposes. It can be controlled from a web browser. My DH can also access it with his phone.
You can program up to 8 pre-set positions which is very handy because otherwise panning and tilting is very slow since the image refreshes after each small movement. We were able to mount the camera in a spot where by panning and tilting we are able to see their food bowls in the kitchen, the area where they sit and watch the bird feeders and their favorite napping spots in the family room, though they don't seem to spend as much time there when we're not home because we usually only see one cat in the family room when we're away. We leave a couple of lights on so that we can still look in on them at night.
To give you some idea of the image quality, here is a screen capture from our camera showing two of our cats walking around in the kitchen, wondering why their bowls are empty. The smaller (320x240) image size was selected here. A 640x480 image size is also available.
Another nice feature of this camera is that you can configure it to email you a snapshot if someone enters the room. We use this feature to get an alert when our cat sitter arrives (or if someone who should not be in our house has walked in!). We don't spy on her but like receiving confirmation that she is stopping by every day.
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A few additional points. Panasonic make a range of web accessible cameras that will work for this application with prices varying depending on the features and the network connection options. The more basic the features and the more restrictive network options the cheaper the camera.
The BL-C10 is several years old and cost under $200.00 but needs a wired connection. The WiFi versions cost a little more.
Depending on where you place it you may need to make a custom mount so that you get the right orientation for the camera. I made one using fexible gas pipe from Home Depot plus some washers and a bolt compatible with the standard tripod mount on the camera.
The Panasonic cameras have a web server built in and the recent ones will auto configure a plug and play router. If you have an old router or firewall at home you may have to configure the port forwarding manually but that is a one-time config. This is required so that you can access the web server on the camera when you are not directly connected you your home network.
If your ISP is prone to changing your IP address you can register with one of several dynamic DNS services like dyndns.org. Again, modern routers will keep that service up to date automatically if the ISP re-addesses your box or you can do it manually or with a client that you run on a PC. That way you can connect to the same name like "kittycam.dyndns.org" and be immune from ISP address changes.
The camera has simple security built in (username and password) and you have several options like turning on the green LED on the front when the camera is accessed. It is configured by connecting to it with a browser.
The web server has a couple of entry points, one that will render the video and the controls for a laptop and another that will render for a mobile device with a smaller static image and camera controls more suitable for a phone keypad. I imagine with the 3G wireless networks the more recent versions of this camera may even do video to the phone.
Really for the money they are good value, the video quality is good and they will give you some peace of mind when away from home.