AppVee writes: "Sentinel is a futuristic tower defense game for the iPhone and iPod Touch. All of us are familiar in some way with the tower defense genre of games and the iPhone is not lacking in that department. Sentinel looks to add to the collection of tower defense games with it's futuristic focus. Earth has made it into space and now must protect itself from the invading aliens that are attacking. The player has 6 different units to strategically place in order to survive the onslaught. There's the laser, bomb, slow, beam, and sniper units for attacking and there is a drone unit for repairing and harvesting resources. "