does mobie phones can build a distriuted system?then they can provide service by themselves,that means apps developers needn't provide a powerful sever end.is it possible?

If course it's possible, just a bit difficult:

You would need to write your code in a way that has vey high failure tolerance, as the users cells (and therefore your computing and storage) would go in and out of service arbitrarily. With limited resources and bandwidth per device anyway, you would need considerable redundancy to ensure quality service. Load balancing / request distribution would also be difficult.

Still, it's possible.

while it's possible I would atleast suggest having a tracker server where the devices can find eachother easily. other than that I guess a data redundancy of 33% would be safe where any 3 devices would have the full information, that number could be less provided that you have alot of users. you would also need some way to verify the data to prevent tampering. so while it's possible it's not really the most pragmatic way to go

What about Batteries? They will die really fast.