With Heads-up, any device can get the heads-up notifications introduced in the Android 5.0 “Lollipop”, no root required. But according to Addictivetips, this app is much more than just a backport. And according to the users, this app is way better than the original!
Heads-up displays the latest notification as a floating popup, complete with full text and quick actions (4.1+).
Works on everything running Android 3.1 and newer.
You're in control: Heads-up has five pages of customization, so you'll get notified your way.
Pocket detection – when you get a message, Heads-up turns the screen on if you take your phone out of the pocket! (Kinda like AcDisplay. Note: this causes a tiny increase in battery usage if you get a ton of notifications)
Privacy on the lock screen (and in general - Heads-up doesn't even have internet permission, so it can't send your private data anywhere)
Oh, and it's known to work on some smartwatches.
– Action buttons on all JellyBeans (4.1+)
– Updated Lollipop themes (again)
– A few bugfixes, tweaks and translation updates