I bought a 'cell phone', and gave it to My Lady. Simply because she wanted one, and felt it was 'safer' for her to have one. I kinda get that, for when she's driving by herself. Myself, I can't stand the damn things, and refuse to be like so many others, led through life by their thumbs.
I used to have friends come over to visit, and in the middle of our conversations (face to face) they'd be whipping out their phones from their 'holsters' and checking what someone else said, and replying to THAT conversation.
I draw/drew the line there. There's a shelf by the door for when they enter. Pick it up as you leave. NOT that hard of a concept to grasp, is it?
As to 'her' cell phone, I don't care because I trust her implicitly and have no reason to suspect otherwise. Add to that, on the (extremely) rare occasion when she's out with a friend or friends, I only ask her to wake me up when she gets home, to let me know she's home. I only ask 'where there any problems?' and 'would you do it again'? The answer is always "No and Yes"....
I trust her with my life and effort, and she trusts me with her life and effort. Teamwork is a mutual agreement and a lifelong commitment.
Anything else is just situational. Establish what marriage means to a person, before committing to that person in marriage.