If you want to spy on a cell phone without access to the phone, the only way to do it is using spyware. But to get started with the app, a user needs one-time physical access to a target device for the installation.
The installation depends on the operating system (Android, iOS). Usually, developers provide the setup instructions for each on their official site. So, customers won’t be lost in the process. Once installed on the target device, spyware allows to spy on a cell phone without having access to the phone.