Unfortunately, there are plenty of situations where having a can of pepper spray could come in handy. Even worse, in most of those situations your state of mind isn't really conducive to remembering important details like the facial features of the person who's trying to mug you, which means the police will have a harder time catching the culprit.
There are a few products that can help you remember your attacker's face while you're spraying deadly poison in his/her face, like this pepper spray phone case. Yes, it could help you take a snapshot of your mugger, but the problem is that taking a photo is just as hard as remembering a face during an attack.
So, some students at Cornell's School of Electrical and Computer Engineering tackled this problem by building the PepGuard, a can of pepper spray that's got a camera and Bluetooth capabilities that are automatically activated when the button is pressed.
After the photo is taken, the device sends it to an Android app on a mobile phone and directs the phone to place an emergency call. The hardware consists of an Atmel ATmega1284P microcontroller, a camera with a high power LED that also works as a flashlight, and a Bluetooth transceiver. The materials for the device cost around $80.
Right now, PepGuard is just a prototype, but it completes the image transmission and activates a phone call in about 8 seconds (or less), and the team plans to make it even quicker and decrease the size of the device in future iterations. Check out the video to see a demo.