Teacher's fantasy: Press a button and your students suddenly have new textbooks in their hands. Amazon thinks it can do this using its Kindle electronic reader. The company has just unveiled something called Whispercast, a free wireless system that lets a teacher's Kindle communicate with student tablets and new books materialize from the ether. Amazon hopes to use this to gain a foothold in the education market where Apple has a head start. Unlike the free-for-all that is the internet, Whispercast is about control.