Raspberry Pi is great for doing crazy setups. Being Linux based platform it can take photos, send emails and other messages over internet. Deddies Lab have shared his interesting setup, where he placed a webcam at the front door and when someone pushes doorbell message with photo footage is sent. First of all he hacked in to wireless doorbell where he was able to capture button press with Raspberry Pi GPIO. Then he wrote a simple Python script to send push message with date and time on event.
During building there came a thought that seeing message isn’t enough as there is no info on who was at the door. The next thing he added was Logitech C270 webcam which was configured to capture snapshots and short movies. Again, python script composed email message with images and videos attached. From this point you could start your own modifications of this system. First of all replace webcam with Raspberry Pi camera and have even more options in capturing images and videos. You could expand functionality by adding motion detector and capture images even when someone is walking around (Actually this is already a security system) or you can think of your own options to it.