Impossible vs. outdated technology...
First of all: Hoshi no koe is an absolutely amazing movie, even more when considering its production process. I find it truly moving and I do like its simple, yet imaginative story.
However, there are some things that really bothered me, mostly concerning the terran technology of 21st century mentioned and used in the movie. I mean come on, who would possibly use cellphones with monochromatic display that are being outdated even right now, when at the same time humanity obviously fights alien invaders with such technology as giant mecha bots and spaceships capable of warp jumps... It could be that author wanted to emphasize the emotional side of the story and so he chose not to use any super hi-tech gadgets that would mess with the process of writing the messages, but still, it just bugged me sooo much... Even the boy Noburu used the same old cellular throughout all the years.
My second complaint would be about the means of actual delivering the message - could it be possible to send a message from another planet, that would have to slice through two atmospheres and eight light years between them, using a regular cellphone? Hmm, maybe with the use of some superpowered radio beam transmitter, but that again doesn't fit in well with those poor cellulars from year 2047...
Finally, when the terran spaceships were leaving for Sirius, they didn't jumped in time, only in space (through this beautifully drawn warp gates). However, Mikako wrote a message to Noburu, stating that next message form her would come in eight years, as if she'd known that she wouldn't return... Because you know, if that was to be hit'n'run mission to attack the Tarsians and quickly drop back to Oort Clouds or wherever, it wouldn't definitely take so many years to do and she would be back in no time, so that her own message from Sirius would reach her much later... So what's the point in writing such message? Could it be some hidden layer in the story about knowing of one's death coming, aka certain suicide mission?
I hope you didn't get lost in my would-be scenarios. The movie is great nevertheless, I just thought somebody might have similar point of view... Gotta go, my cell's ringin' :)