You can use Amazon Echo or Google home mini as an intercom system. I have one in the kitchen and one in the living room. It is useful to say "Alexa announce dinner is ready", when DH is watching TV and can't hear me call.
Our BT landline phones have an intercom button.It’s quite a small button but at the bottom of the handset so hopefully would be ok for your husband as he wouldn’t hit another button at the same time.We found them really useful after I had knee surgery as we could call each other at the press of a button.
Does anyone have experience of buying some sort of intercom between patient and carer, round the house? I've seen alarm systems for people who are alone but we need something for my husband to call me in our long narrow house, when I can't hear him call or ring a handbell. We have mobile phones but he finds it hard to make a call and needs to just press a button. I looked at children's walkie-talkies but the buttons are tiny. Any ideas?