It's important not to forget that the 770 and N800 are *Internet* tablets. In the first instance if I were developing something like this I'd go for creating a service I could connect to - think media server style. Much easier to do the development that way. It might even create a better product - you could speak into one 770 and your father could read on another.

It might be worth suggesting such a product/service to these folks - http://www.spinvox.com/