The BTKeychain is MSP430-based keychain with a Bluetooth interface and a buzzer. The device is very useful for people who never remember where they put their keys. The Bluetooth interface is always discoverable. Thus, if you want to find the keys, you can search the Bluetooth name of the keychain from cellphone, and then connect to it and make the buzzer beep.
The project’s board comes with Bluetooth chip that includes an internal aerial, a MSP430 microcontroller, a battery charger and a low drop-out 3.3V linear regulator. It uses 180 mA/h LiPo battery as power source and cheap photo frame key chains case for PCB housing.
Doragasu, project designer, said that any open device with a Bluetooth interface can be used to make the keychain beep. He has coded a script that can be used for this task with any GNU+Linux PC and J2ME Java application for Java enabled phone. Similar scripts/applications can be developed for Windows, OS-X, Android and iOS devices.