There is little scope to differentiate a new Calendar application from the existing products like Outlook Calendar, Google Calendar, and iCal while just implementing the standard is still pretty hard. The same problem of standardization seems to have plagued products focused on email, calendar and RSS feeds. The only exception to the rule is producing premium quality products, either in reality or perception and then wait for a niche market which will be willing to pay a premium hoping that they are getting the best product, for example, 41$ mini-USB cable and a 50$ MailMate email client.