I'm afraid as you guessed it, iOS-only for launch on Jan 10th but we want to get Android and web as quickly as we find product market fit (PMF). This decision is so we can iterate and improve the product based on our users feedback as quickly as possible, the more platforms we support the slower can move. We suspect though we're going to hear this a lot more and PMF for a new calendar service might only be possible with apps on all your devices!