That's weird Beginning, my DH won't use a mobile either. And won't call me on my mobile. I actually gave up having one a couple of years ago (other than my work one), but got a new one when he got sick last year as a way for his kids to talk to him in hospital (they all live in other countries so also have time zone issues) and for him to get me in an emergency.
No way no how can/will he use it. I'm not sure which.
When the kids came back we tried together to get him to use a mobile (using contact with the kids as 'bait'
) Didn't work. Either he thinks it is a conspiracy to make him pay more for the privelage of a phone call or he is having trouble learning new technology (I got him an ultra simple phone which he did manage to work a couple of times, but still handed to me when he finished a conversation so that I could hang up for him). It had a big red button for 'end'. I have read that 'they' are designing mobiles specifically for 'old' people now but I haven't seen anything on the market yet. The pictures phone sounds wonderful.
Not trying to hijack your thread n2e, but I would be interested to see how your DH adjusts to the mobile. I thought I was introducing another safety measure but it backfired. Of course, you are thinking of calling him instead of the other way around which is very worthwhile.
I do know that my SIL who is getting quite advanced in her dementia can always manage to dial a prominently displayed phone number when she needs help, which is why I suggested writing the number on your board. We also do the crossing off days thing which is a tremendous help to her.