Cameras with SD Card Recording
While it used to just be that you'd have to record footage onto Network Video Recorders, security camera technology has reached the point where every security camera is now equipped with a CPU, SD Card, and efficient firmware. These tools allow the camera - if the user so decides - to store footage directly onto the SD card itself instead of going off to a video recorder.
Now, this isn't a foolproof or vandal-proof form of saving footage. If somebody steals the camera, you will lose all your security camera footage that had been stored on the SD card. However, if you are able to comfortably ensure that the camera isn't ever going to be stolen or take unforeseen damage, then the SD card is perfect. A single camera secretly placed into a potted plant watching your front door, for example, is a good fit for this model of recording footage. All you need to do is plug in the SD Card and manage the port forwarding settings on your router. After that, you are ready to use a stand alone security cameras both as a video recorder and as a camera.