Many cameras will do what you need to do. The question is do you have the time to monitor the camera all the time or do you just want to be notified when there is motion? I suspect the latter. Depending on your situation motion detection can be a tricky thing (is the light consistent, how big of an area, etc).
I have some panasonic wv-nm100 cameras which have a web interface and built in motion detection that will upload a picture to a FTP server when activity is detected. The images could be hosted offsite and accesible via the web. I dont use the built in motion detection but instead us a piece of software called zoneminder ( www.zoneminder.com ) which has very flexible motion detection and image archiving.
If you just want to watch a live feed there are a number of ways but be careful of where you watch from. Some of the active-x and java solutions use ports that are not open on many corporate firewalls.
This is what I would really like to get to ... Once the sensor is tripped, you are notified via mobile phone and can monitor the video and talk to the intruder ... this is a demo of linux mce
http://video.google.com/videoplay?docid=2176025602905109829#22m06s