PlayStation 3 consoles were combined to make a super computer. Can the Android phones be modified in the same way? Could I use the processing power of 2 phones to play a movie that 1 would not.
It depends on the workload but you absolutely could use Android phones as a cluster in much the same way they did with the PS3's.
You'd probably need some sort of server-client setup. With a server setup to manage the clients, assign work and manage the overall process and the clients setup to complete the work.
This is an interesting idea, for sure!