Sentinel 3: Homeworld is described as '- the third instalment of the highly acclaimed Sentinel sci-fi tower defense series!'. There are six games similar to Sentinel 3: Homeworld for a variety of platforms, including iPhone, Android, iPad, Android Tablet and Windows Phone. The best alternative is Robo Defense, which is free. Other Sentinel 3: Homeworld like games are HexDefense (Freemium), TowerMadness (Paid), Radiant Defense (Freemium) and TapDefense (Free).
Tower Madness is an epic 3D tower defense game for iOS. Evil aliens are coming to turn your beloved sheep into intergalactic scarves-- you must protect the flock using only quick thinking and the arsenal of upgradeable weaponry at your disposal.
Radiant Defense is a tower defense game set in a vibrant universe invaded by countless alien hordes. Build your space fortress any way you wish, set up wide variety of weapons and traps and let the invasions begin!
WOW! Saturn Defense is such a cool 3D defense game! NOW Free! Get ready to DEFEND THE SATURN from the invading aliens! The most amazing full 3D tower defense game from SpiceSpin Studios! Full 3D defense battles with gorgeous space background will hook you for hours!