Problem is that it's very difficult to find the hashing algorithm that would be really ASIC resistant, not to mention GPU. For instance, Primecoin which included large integer algorithms that should be difficult for GPUs was soon transferred to GPU mining. All scrypt algos are prone to GPU mining. I tried to find some hashing algorithms that would favor RISC processors, since they dominate modern smartphones, but I've failed to find any. If anybody has some info about such algos it would be very nice to share that info here.