Stan has a VueZone WiFi security camera. He says it's easy to install and works great. Leo says while it's simple to install, the VueZone won't screen continuously, nor could he record from it. It can only be powered when it's being accessed.
DropCam is a good always-on option that not only records, but allows users to go back in time over a few weeks and see everything that's happened. If he just wants a camera that he can access when someone's at the door, though, then it's a fine option.