How good is the service from your current mobile provider? This app tells you by showing signal strength and download speed in all the locations that matter to you. You can use your second SIM to compare this to another provider. The results across all the locations are recorded on your mobile. The app also shows much of your data and calls allowance you use: maybe you could move to a cheaper plan? You can also test your WiFi and decide whether you could replace your fixed line with a mobile-only service. This is an ad-free service and does not require registration.