For Google Calendar sync using this tool: https://trellocalendar-francois2metz.dotcloud.com/# Just add new "other calendar" and put there the ics link from tool (ICS Feed)
Caution: It updates each few hours, so do not panic if you change something in trello but it doesnt change in google calendar at once
Before: You done first step and you have a ics link from tool
1. Settings -> Mail, Contacts, Calendars -> Add Account
2. Select Other -> Subscribed Calendar. Paste ics link from tool without this symbols [only_me=false¬_archived=false] in the end of link, after [ics?]. If you want alarm you can live it [&alarm=-PT0M]
Example of link: https://trellocalendar-francois2metz.dotcloud.com/calendar/blablabla/my-board.ics?alarm=-PT0M 4. Touch Save
Cautions: It updates automatically, just try to wait for a minute or open close calendar app in the iPhone.
P.S. All your ideas and question about trello + google calendar sync you can ask here: trello.com/card/ideas-enter-a-comment-here/4f0d53d03ca0f7f83f03cad0/4