This is an experimental plugin - it seems to be working fine, but I'm not sure how useful it is to you in its current form.
Cynical Calendars lets you create Indigo triggers that fire when particular types of iCal events happen - when they start or end. Every time you create such an event trigger, you can specify conditions for matching iCal events - a calendar, regular expressions for the title, notes, and location, and some filters on the event's nature. Any time a calendar event starts or ends that matches all these criteria, your Indigo event fires and lets you do whatever you feel like doing.
Cynical Calendars hooks directly into your Macintosh's Calendar Store. It can monitor anything that you've told your Mac's calendar about: local calendars, iCloud calendars, shared and imported calendars, arbitrary CalDAV calendars, even the silly little birthday calendar - they're all yours to use with this plugin. And yes, if you add a calendar event on your iPhone or iPad, Cynical Calendar will pick up on that and (if it matches) execute your event triggers.
There's an innocent little checkbox that tells Cynical Calendars to take the Notes field in any matching calendar event and execute it as Python code when the trigger fires. Yes, this does exactly what it sounds like - except that the Python code is actually running in the context of a plugin formula, so that you can "pick up" Indigo constructs like variables directly by name. See the separate thread on plugin formulas for more information.
What would you use this for? I'm... not sure. That is why I'm putting it out for you in this rudimentary form - have a try and see what sense you can make of it. You could use it to program Indigo from iCal (or any calendar program on your Mac or iOS device). Or you could keep all the programming in Indigo and use the calendar as a time code generator. Or you could simply use it to integrate your house into your well-arranged calendar schedule. Or you could surprise me with something altogether more interesting than those...
Anyways, let me know if you run into any trouble, or if you find a way to make this plugin be useful to you and your house.
More information and download from here: http://www.cynic.org/indigo/plugins/online/ical.html
Cheers
-- perry