WOMAD 2011 Festival is over 30,000 attendees and used the Triangulate engine for their event.
It allows users to view their realtime position updated on a PDF map. Users could set reminders for their favourite bands and would be shown on the map where they need to be to view the artists.
The app also had a live video feed for anyone unable to attend the festival.
Each artist had their own twitter, youtube and web page available along with their biography which was available even when offline.