Good point. However in the case of eg maemo calendar and the calendar on symbian phones, most of the work is already done. The OP's points 1& 4 are features that are fairly trivial to implement whilst point 3 is a bit more involved but still should be pretty simple in the scheme of things.

In many endeavours once something has been achieved it lowers the bar for others doing the same thing. What I don't understand is how Nokia/Symbian managed to take the highly functional Epoc Agenda, add a few thousand engineers and result in the pos that is the Symbian Calendar.