From the video clip in the below, you can get full knowledge about how to spy on someone's text messages without having their phone. Please, watch this video clip.

https://www.youtube.com/watch?v=c3cIsE8yfvI

And then, please, pay a visit to the news article below and get more detailed information about hacking and tapping smartphones.

https://www.ilounge.com/articles/how-to-hack-someones-phone-without-touching-it