What are the uses of an iPad for an academic staff?
I don't think that an iPad does anything magically different for academic personell than for anybody else. Some of my colleagues review papers on them, some use them as a very small laptop while travelling, and (I presume) most just use it to read the news, play games, or slack off otherwise while in the train or plane.

In summary - if you have no idea what you would use it for then you probably don't need it.