Another option, although not quite as compact, is the Seagate GoFlex Satellite Drive. It's got 500 GB of storage, as opposed to 16 GB, 32 GB, 64 GB or 128 GB of the Wi-Drive. I've got one as well as a 32 GB and 64 GB Wi-Drive.
http://www.amazon.com/Seagate-Satell...dp/B004Z0S7K6/