Are there any mobile application for conference attendees? I'm currently attending a conference, and considering that (almost) everybody has a smartphone, but not necessarily an Internet access (because of roaming charges), it could be nice to have an application that could cache the program, the local map, the list of attendees, that could be updated with program changes. 

Does anyone know such an application? Ideally, that should be a "meta"-application, that could be instantiated for specific conferences (a bit like Easychair).
Conference4me will do this more or less automatically. It displays the conference schedule including talk titles, authors, and abstracts, as well as maps of the venue, the list of participants, and other information. All this can be browsed offline but the app will automatically update it every several hours if it has an active internet connection. You can add sessions to your agenda and the app also makes it reasonably easy to add them to your calendar system of choice (at least it works with Google Calendar on Android).

However, the app's functionality depends on some cooperation from the conference organizers. For starters, it can only pull information from Indico, EDAS, and OpenConf, so the conference has to be organized using one of those systems, and all the relevant information has to be uploaded. Additionally, the conference organizers will have to ask the app's developers to manually set up the link between the conference website and Conference4me's data stream. It's apparently not a very involved process for the organizers, but you can't just download the app and immediately use it on any arbitrary conference with a website.