I hacked a simple audio recorder and playback system, rigged it to Arduino, and inserted it into a tin can phone that I installed by the door.
To record a message, press a pressure sensor on the outside of the can and speak into it. To listen, simply hold the can up to your ear. (It uses a light sensor to trigger playback!)
My ulterior motive was to learn how to hack existing electronics and control them with Arduino. It can be adjusted to use different sensors and be put in any sort of housing. I uploaded a quick demo for now; fuller video to come soon!
I am a maker. As founder of MakerBlog, I enjoy sharing ingenious creations with others! I also enjoy the random and unique!