All of Big Daddy's Creations' iOS games are now on sale--several are worth checking out.
First--Army of Frogs HD is free. This is not a great app, but for the price, it's a green light.
Second--Caylus is on sale for $2.99 (normally $4.99). If you want to learn how to play the game, go get it, then head to Ryan Sturm's How to Play podcast to get the "how to play" and "how to win" episodes. If you love the game and don't have the ioS version, it's also recommended. Other than that, it's at least worth considering, just know that the AI isn't very strong and that multi-player in practice doesn't work very well. Yellow light. (This will also be one of the games reviewed in a forthcoming, but yet to be recorded, set of reviews.)
Finally--Neuroshima Hex, its armies, and NH Puzzle are on sale. Good implementation. I think I gave the original a green light a couple of years ago, but would probably say it's yellow now just because there're so many other great game apps out there now.