Unit9 Games today announced the very first game for Android Wear. SWIP3 is powered using the Unity 3D engine and is "the very first Unity3D game specifically developed for AndroidWear." It is 18 MB in size and runs on Android 2.3 and higher. SWIP3 isn't free though; you will have to shell out $1.69 (Play Store) for some entertainment on your wrist (Samsung Gear Live or LG G Watch).
SWIP3 is also playable online for free here.