I released a new free game recently - Evil Monkey Touch Defence. You control a "good" Evil Monkey / King Kong type character, his job is to try and protect the tower from incoming missiles!
This was an experiment in creating the simplest possible control scheme for a casual game, while still making a game that's good fun to play. When you touch the screen the monkey starts dropping his aim, when you release the screen he fires. No buttons, no tilt, no nothing, just touch and release anywhere on the screen to control the game - it couldn't get any simpler! The longer you survive the faster the missiles get, and the more missiles you destroy the higher your score, simple and addictive fun...
You can check out Evil Monkey Touch Defence here. I'd love it if you would leave a nice rating or review if you like the game :)
On the subject of free monkey based casual games for android... A friend of mine recently released his first game, you can check out his Monkey Game here - it's a fun casual physics game that uses Box2D behind the scenes. There's nothing in the least bit evil about this monkey, he just wants to eat his fruit (and not get eaten by a croc!)