FamilySearch International has released a new iOS application, FamilySearch Indexing. It’s a free app that does exactly what the name implies – it helps to index genealogy-related information on FamilySearch’s genealogy database. It can display images from genealogy/historical-related documents such as certificates (birth, marriage, death), census information, immigration records.
These are snippets, and the idea is that you view these snippets, and then transcribe them (index/take note of what they say), and then the application uploads the information to FamilySearch, at which point it is added to the genealogy records at FamilySearch.org.
It does not just rely on what you transcribed – others can transcribe the same document or snippets of documents, and it then compares them to make sure that they match.
You do not need the desktop version of the FamilySearch indexing software.
Update: You do not need to be a member of the Church of Jesus Christ of Latter Day Saints – see the comment that follows.
Also, there is a FamilySearch Indexing for Android app.
* iPhone, iPod touch, or iPad running iOS 3.1 or later