Hatch Sleep Machine
My dad was 9 miles down the highway when he realized he'd left his Hatch sleep machine at home. He turned around and drove back to get it.
That tells you everything you need to know.
I've had mine for years (ironically, my parents gave it to me as a birthday gift — and now my dad is obsessed with his own). You set up a completely custom routine — warm light and music while you read, a sleep meditation when you're ready to drift off, then white noise the rest of the night. You can even set it to wake you up gently in the morning.
It's one of my all-time favorite things I own. If the dad in your life struggles with sleep at all, this is the gift.
$169