About availability in countries and stores. This is actually a much bigger and much more difficult task to accomplish than gathering information about ereaders. Moreover, this should be an automated task, as it would be impossible for me to track daily prices on hundreds of sites manually. I'm still researching ways of how this can be done.
As for currency converter, I think it's a good idea. I think I can convert the price to the currency of the country where the person is coming from automatically. I will put this on my todo list.