Your smartphone has a built-in scanner that allows you to scan documents and save them as PDFs with ease on both iPhone and Android.
You can use your smartphone as a level to hang picture frames or shelves straight by using the Measure app on iPhone and searching for 'bubble level' on Android.
Sharing Wi-Fi passwords between iPhones can be done by holding them near each other for a prompt, while Android users can share via a QR code in Wi-Fi settings.
Both Android and iOS have a hidden feature that allows you to resize and move the keyboard to make typing with one hand easier.