There are two ways to get the app on an Android phone. Google Play is the easiest, and keeps itself up to date.
Install Never get caught short from the Play Store like any other app. It updates itself, and it is the only version where Supporter can be bought.
Open in Google PlayOpen this website in Chrome on your Android phone and tap Install app when it offers. If you do not see the prompt, tap the three dots in the corner and choose Add to Home screen.
You get the same app on your home screen, it works without a signal, and it updates itself whenever there is a new version.
Open the appEvery item, note and appointment lives in the storage on your own device. There is no account to make and nothing you enter is sent anywhere. If you turn on backup, what leaves your phone is already scrambled, and the key never leaves the phone, so it cannot be read by anyone, including me.