As a backup mobile phone: use an idle mobile phone as a backup mobile phone, and use the backup mobile phone when the main mobile phone has problems or needs to be recharged.
As a learning tool for children: install some educational applications on idle mobile phones so that children can learn knowledge by using mobile phones.
As a smart home control center: install smart home control software on idle mobile phones, and you can use mobile phones to control smart devices at home, such as lighting, air conditioning, music and so on.
As a music player: If you use an idle mobile phone as a music player, you can connect it to speakers or headphones and enjoy high-quality music.
Be a camera: Take an idle mobile phone as a camera, and use the camera function of the mobile phone to record the beautiful moments in life.
As a game machine: install some game applications on idle mobile phones, and you can play some casual games with your mobile phones to relax.
As a reader: install some e-book applications on idle mobile phones, which can be used to read e-books and expand knowledge.
As a fitness recorder: install some fitness applications on idle mobile phones, and you can use mobile phones to record health data, such as steps and heart rate.
As a travel navigator, you can use mobile navigation to help yourself travel better by installing some navigation applications on idle mobile phones.