The best approach to this problem would be for Rio to add USB-master support to the software in the Karma (hardware already present), and then sell a USB host dongle for it, with driver support for some common USB slaves such as USB-ether adapters, USB-mass-storage, etc..

But I suspect the underlying O/S is not up to the task -- it's not Linux, so drivers are probably quite hard to come by for such non-essentials.

Cheers