Many years ago I gave one of our team an official licence to nag - literally a licence on a card to 'nag, cajole or remind'.
I did it with humour, but a serious purpose.
Checking by a human is an efficient way to back up written or electronic systems, particularly those involving follow-ups. Of course, you have to choose someone with advanced people skills.
Make sure the whole team knows what you are doing and be sure that you've been successful selling the benefits of an in-house nagger.
You might want to make it a temporary appointment, say for a project, or rotate the role.
Our colleague is still with us, diplomatically asking questions like, 'Have you had a chance to...?'
I'm one of her regular nagging targets - and need it as much as anyone. I know that if I leave a follow-up call, she'll be on my back: 'Any progress with...?' It's better to be ready, 'Sure, all done. Let me tell you how it went...'
No one takes offence when she nags. After all, she's licensed and a good nag (in the best possible sense) helps the whole team.