You can use NFC tags (driver's licenses, commuter passes, ID cards, electric money card etc.) as "Keys" without which you can't stop alarm sound.For example, putting your card in the bathroom or on the dining table prevents oversleeping and sleeping again.NFC alarm works correctly with FeliCa and Mifare cards. Other NFC tags are also available, but some apps are configured to start with specific types of NFC tags. If you have installed such apps, they starts prior to NFC Alarm and some tags can't be used in NFC Alarm.