The AA's VIxa app uses a device that connects to the OBD port in your vehicle to collect data about the vehicle's health, which is then displayed in an app. It can also provide driving data that scores your driving style. It could potentially detect issues with your vehicle at an early stage, although if this were to happen you would still need to take the vehicle to a garage for it to be inspected. If your mechanical knowledge is limited and this would provide some reassurance regarding the condition of your vehicle then it may be worthwhile.