I picked up Baby Elephant Ears on a whim. I was in a local baby-product boutique to return something, saw them, and bought them (in the style below) because I thought they were cool. They ended up being quite useful, too, I'm happy to report.
Here's what they look like on their own:
Rainforest Bouncer when he was teeny-tiny:
So you get the point of them, right? They're for head support when your baby is just a newborn and his head's falling all over the place. I used them with Baba G in the bouncer, his car seat (both in the car and when it was attached to our stroller), and in his MamaRoo (will write that crazy thing up soon).
As you can see from the manufacturer's web site, they make them in more designs than you could possibly imagine.
The bottom line: A useful product, but you'll likely only use it for a few months. Baba G got too big to use the Ears in his car seat/stroller very quickly (because his car seat already had built-in head support, so the Ears crowded him too much). They were helpful for the bouncer and MamaRoo for a month longer, but he was definitely done with them by his three-month birthday.
Worth $21 for a few months? They were for us, but might not be for you, as you can definitely achieve the same results with some rolled up blankets or other means of head support. However, Baby Elephant Ears might make a cute shower or newborn gift, especially if you don't think the new parents would splurge on a non-necessity such as this.