Installed in the car battery Real-time Monitoring Through Mobile Phone APP (Free app for both iOS & Android). Receive notification of battery conditions when enter Bluetooth range. Show voltage & charge info. when user is to the vehicle,no need open app. Automatic synchronization when enter Bluetooth range. Check starting(cranking) system when each time engine started Check starting voltage each hundredth of a second when engine is starting. Support: All 12V Car Battery Available: Android 4.3 and Later IOS: IOS 7.1 and Later For : For 4s and Later For : For 3 and Later Language: English Connection : Bluetooth Colour: black Material: ABS Size: 17x13x2CM Package Contents: 1 * Battery tester Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.