I tried to make popcorn with three Nokia cell phones but the test failed. The kernerls were not even hot so it may be that some of the similar videos in Youtube are faked. However, it is possible that the phones must be in the right channel and you need more phones.

I tested to make popcorns with four Nokia cell phones but it did not succeed. Popcorns were not even hot after the task. It may be that one must have phones in right channel to pop popcorns or more phones.