For those living or travelling in Japan, you can now get Vocaloid events from VocaDB in your Google Calendar, including mobile phone (tested on Android, should work in iPhone as well).
For Google Calendar and Android, the instructions are as follows:
Open your Google Calendar. Select “Add other calendars” by pressing the “+” next to “Add a friend’s calendar” field. Select “From URL”.
Enter http://ical.vocadb.net/events as the calendar URL and press “Add Calendar”.
VocaDB events will now appear in your calendar! If you enable sync to your mobile device, the events will appear there as well.