A possibility to synchronize with mobile devices.
When using the calendar as a reporting tool for service personel, it would maybe necessary to have an offline function for the reporting.
In my country, there are nearly no "black holes" so a such function would not be neccessary, but where "black holes" often occurs, it might be needed.
And then there are the syncronization issue.
I don't know if there could be a solution to this.