How can you tell me when someone else's mobile phone is turned on?

There are two ways: first, set the SMS report in the mobile phone to open, and then send SMS to the other party. You won't receive a message report when she is turned off, but when she is turned on, your mobile phone will receive a message report immediately, so you will know that her mobile phone is turned on. (It should be noted that if your short message has been sent for more than 48 hours, it is recommended to resend it. )

Second, subscribe to the mobile phone "Radar Dog" SMS service, but this service is only for China Mobile.