My greatest piece of sleep tech is the Do Not Disturb function on my phone. I didn't bother with it until the time my brother sent me multiple texts at 4am talking about how great Nicki Minaj is. True story.
But really, blackout curtains controlled by an app would be incredible for me. I'm a super light sleeper and any little sound wakes me up, so something to help with that would be great. But I don't do well with sound machines.