How about a setting which allows the user to nominate a set time of day / once a week where if there are new voicemails, your phone rings and a message alerts you to the fact?
We have a phone with no visual indicator and sometimes miss messages for days (both out at work and don't remember to check the landline every day).
I'd love to set it for 'Every day at 6:30pm' or 'Sundays at 5pm'
Then the phone would ring and the message would be something like 'Hi, this is TalkTalk voicemail, with your scheduled alert. You have two new messages. First message......"
The best version of this would be to go straight into messages (as opposed to a message telling you to ring Voicemail)