The World Register of Deep Sea Species (WorDSS) just released Deep Sea ID a free iOS app that allows offline access to the taxonomic information for over 20,000 deep-sea species. The app works on both the iPhone and iPad allowing you to dial into more details on these fascinating deep-sea creatures.
The mobile app is tied to the main online registry that was started in late-2012 as a project of the International Network for Scientific Investigation of Deep-sea Ecosystems (INDEEP) to build a comprehensive database of known deep-sea species. The mobile version features over 350 high-resolution photographs of deep-sea specimens as well as links to online taxonomic tools, sources and important references.
The interface overall is relatively simple that allows you to search by full scientific name, epithet or common name. Overall the app is a fantastic and portable scientific tool for deep sea species but not too handy for the average hobbyist. Yest, since it is free, it is worth a download and learning a bit more about the deep.