I can't even tell you how many times I've gotten an 'Are you close? Where r u?' message when it's obvious I'm driving.
I could understand it if I were running late, but I'm almost never late... and, I always send a message the day of, confirming any details, and saying that I'll let them know when I'm about 5-10 min away.
If they want banter (or even chat), I rarely answer. Even if I'm NOT driving, that type of thing tends to get out of hand really quickly. For instance, I recently had a client text me for 3 hours straight. I'd replied in a quick and friendly way to an appointment request. Then, he just kept on going. I finally had to tell him that I was leaving to drive someplace... oh, and guess who ended up never replying to my confirmation email? LOL. (That's happened twice w/the same guy.)
Unless it's clear that both parties are available for and receptive to texts, they should be confined to the essentials (room number, 'I'm running 10 minutes late,' etc.).
I'll usually send the guy just enough to reassure him that we're still on, and that I'm all set to arrive on time. If he's visiting me, I'll sometimes text the room number and tell him to come right up when he arrives, etc. But that's it.