While I like the idea of tabule, I think not targeting Android in education oriented apps is a mistake. A lot of students don't necessarily have enough money to shell out for an iPhone, while cheap Android phones are everywhere (at least that's what I see in the UK).
Absolutely. We wanted to get the iPhone app out the door, but we definitely have plans to build support for Android too. In the meantime, we do allow students to use Tabule over SMS. It's not the same, of course, but works for a temporary measure.