There are several Internet surveillance cameras which work very well for this purpose.
The camera is connected to the Internet and takes a still picture on the schedule of your choice (once an hour, certain hours, certain days [built on the premise of UNIX CRON]), then sends the picture to you (e-mail or FTP).
It is all automatic. The cameras cost in the $200 range, with the built in software to do the scheduling and sending.
I did this for my alma mater University in 1999. The camera pumped out 1000s of still images, which I made into a slide show.