TAPP 2 Click uses Bluetooth to trigger a notification on your iOS or Android device. Register your filter in the MyTAPP app, then just press the TAPP 2 Click green button to trigger a notification on your device letting you know your current filter status, how long until a new refill cartridge is required and how many plastic water bottles you have avoided to date.
TAPP 2 Twist is manual. You can register the filter in the app if you like. But you can also just twist the calendar to set it to 3 months from today (or the day you replace the refill cartridge). The filter has a calendar on it, which reminds you of when you need to replace the cartridge