Most phones power down NFC radio automatically when the screen is turned off. Golf Pad uses SmartLock mode to keep both screen and NFC active, while blocking on-screen controls to avoid accidental inputs.You can also see the distance to the target and change current hole right in SmartLock mode, without unlocking the phone. However the screen is dimmed to maximize battery life. Please see this page for Android and this page for iPhone for more information about using SmartLock during the round.