Between to-dos and calendars, there's Superminder
The strength of Superminder is in its simplicity. The most obsessive modern design gurus will love the look and intuitive feel of the UI. The only thing I can knock it for is that you have to pay for SMS reminders, but even that isn't the worst thing. SMS shortcodes are obscenely expensive, and designer geeks have to eat. Plans range from $4 for 15 SMS messages to $25 for 100, or you can always use Superminder via email for free.