Abstract: A portable power source and control device for a mobile phone or tablet is releasably attachable to a user's key ring or key chain and sized to be carried in a pocket or purse. The device has an internal rechargeable battery to provide emergency power for operating the user's phone, USB connectors for connection a power source and the phone, an internal microcontroller, and a Bluetooth® wireless communicator. A user actuator generated a locator command causes the phone to ring to indicate its location; and a locator command from the phone causes the device to emit a sound to indicate the device's location. The device can determine and indicate via LEDs the charge level of the battery, and has flash memory for data storage and transfer between devices.