It is necessary to have a in your vehicle. It will remider you of when you are driving too fast. Built-in 3.7V 5000mAh Li-ion battery Support standby time up to 90 . Sending "Monitor+Password" to the device first, then the device will turn into monitor mode, now if you make call to the SIM number in the device, it will pick up your call automatically and you will can monitor the voice around the device This alarm works only under continuous positioning mode.When the unit is exceed the you presetted, it will send message speed alarm to the admin number every 5 minutes. After you did the shake alarm setting,please keep the being stationary for 5 minutes, then this function will start working. It will send SMS sensor alarm to the admin number when the unit get shocked. Feature - Color: Black. - Material: Plastic. - Size: Approx. 8.5 x 7.5 x 3 cm. - Built-in 3.7V 5000mAh Li-ion battery Support standby time up to 60-90 . - There 5pcs built-in magnets,with super strong powerful magnetic,can be very easily installed. - Send "Monitor+Password" to the device first, then the device will turn into monitor mode, now if you make call to the SIM number in the device, it will pick up your call automatically and you will can monitor the voice around the device - This alarm works only under continuous positioning mode.When the unit is exceed the you presetted, it will send message speed alarm to the admin number every 5 minutes. - After you did the shake alarm setting,please keep the being stationary for 5 minutes, then this function will start working. It will send SMS sensor alarm to the admin number when the unit get shocked.