I personally do not see a problem with an occasional text between the trainer and the client, so long as personal space and preferences are honored. Not everyone uses texting, but then again a lot of people have come to depend on it for “immediate communication.” Respecting the technology, I use texting with a client to send reminders, confirmations and “yes” perhaps even asking if they are well. That being said, I do NOT overdo it, nor do I do it without first obtaining my client’s permission or in direct response to a text from them.
Whether it is considered “weird,” and when it crosses the line in my opinion is when it is unwanted, or obtrusive.
I hope that this helps.