Home surveillance suggestions

I would like to set up some kind of system in my home to keep an eye on some workers who will be in and out of my house. I would like this to be covert, so I need some suggestions on small hidden cameras or systems.

I tried a very small 1.2 ghz camera and was very unsatisified with the results. I could not get it to focus on anything more than a couple of feet away and it required that it be hooked into an outside display.

Any suggestions?