Dear James,
If you need an offline Sanskrit dict for OSX there are several options.
With an app called DictUnifier you can turn stardict files into mac dictionary files and search them from Apple's native dictionary app. It is quite convenient and useful, with many dictionaries available (MW, Apte, the Pali Text Society dict, etc.):
You can also use the Kotonoko app, which has dictionaries available for MW, Apte, Tibetan dicts, and many others:
You can even make the Köln online MW dict available locally on your hard drive for offline use:
Additionally, while I am quite pleased to see this new iOS dictionary, I'd like to point out that there are several Sanskrit dictionaries available in the app store for free in case anyone wants to save $5 (not that this is an expensive price for the convenience of these dictionaries in your pocket!).
Best wishes,
Charlie