is it a sin to check messages etc while at adoration? what about while in a church when there is no mass or adoration?

No and no. I wouldn't encourage it at adoration, but it's not a sin.

Why would it be sinful? Maybe you're waiting for important news, someone in your family is sick and may die soon, you may be waiting for a call back from a potential employer after a job interview, there may be any number of things, I would these distractions are things you should pray about during your adoration time, I mean, if the messages are something trivial, 'we're going to the movies tomorrow night, what movie are we going to see?' those messages should be ignored as much as possible, I'm not going to say you should pray about that, but if the messages are significant, then use the message as a reminder that you should pray about that issue.

I didnt mean in the sense of waiting for an important message. I meant like casually remembering "oh, I need to check my bank balance" and sitting there like it's your home office sorry I wasnt clear

Like I said, probably not a good idea, but not a sin unless it's intended to show irreverence.

A sin? No. Rude? Definitely.

If one believes they are encountering God during Adoration it seems considerably more than impolite that said person thinks it more pressing to check on the mundane things of life than to experience The Lord.

One of my daughters used to text on her cell phone while talking to me. After a few times of this happening, I stopped talking while she was texting.

She said, "It's OK Dad. I can talk to you while I'm texting."

I said, "That's OK. I'll wait."

She got the message.

But why do you feel compelled to check your balance? Are you having financial problems? That sounds like should pray about. See what I mean? Instead of feeling guilty for no reason, ask yourself why you are doing what you're doing. There is probably some deep seated worry, concern or anxiety that is driving you to do this, so pray about that anxiety. If you dont know why you do it, pray for the wisdom of self knowledge so that you can find out. Don't beat yourself up, you don't accomplish anything by doing that!

thank you

I can use a cell phone during the adoration for reading the morning prayer.

Some people have a wandering mind. Just put those thoughts aside and try to refocus on adoration. I can be watching a movie, and suddenly realize I was thinking about something so intently that I missed part of the movie. The same thing happens when I'm praying the rosary. I have ADHD, and it's really hard to focus, or sit still for even a few minutes.