I've heard of these, but don't own one. Is the dolphin the equivalent of the Duolingo bird, or were you making a joke? (Sorry to ruin the joke if you were making one, I was just curious!)

Closer to a Tomagotchi. It's just some cute little pixel animations. It "levels up" as you use it, and has a mood based on frequency of usage, and randomly rotates between different activities. It doesn't affect anything the device actually does, it's just for fun.