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 . when user is close 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 method: 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 cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Sold by-YJL official store