I am looking for a tower defense game for Android that supports two human players (either collaboration or 1 vs. 1). I use Samsung Galaxy S3 with Android 4.1.2 and Nexus 7 with Android 4.4.2. Each player would use its own Android device.
I found Bloons TD Battles:
Test your tower defense skills against players from all over the world in two awesome game modes. In Assault Mode, you balance your income between building defenses and sending groups of bloons at your opponent. In Defensive Mode, you don't send bloons directly and instead outlast your challenger against endless waves of bloons. Either way, the last player standing wins, earning Medallions that will unlock new monkey towers, powerful upgrades, and cool bloon decals with which you can customize your attacks.
If you are new to Bloons tower defense games, don't worry - a helpful tutorial walks you through the game, and matchmaking will help balance the opponents you face. And if you want to battle against your friends, you can easily create and join private matches with anyone on your Facebook friends list.
Unfortunately you can only play against each other, as far as I know.
It supports Android 2.3 or higher, so that shouldn't be a problem.
EDIT: I found it! Toy Defense 2 ($0.99, also has free version)
- Your Facebook friends can help you in battle and become heroes under your command
Toy Defense 3 ($1.99, also has free version) also supports playing with friends. And not only that...
- Invite your friends to join you in a magical world!
- Cooperate or compete with your friends' courageous knights