I bought an Acer Netbook for less than $300 USD that runs any of the popular DAW software and conveniently connects to the Gi via USB.
There are 'class compliant' USB-MIDI adapters with a USB connection on one end and 5 pin DIN MIDI connectors on the other end that will work, but I have found them physically awkward and cumbersome and can put quite a strain on the iPad's connector, to say nothing of all the cables draped across the top of the keyboard. Since the iPad operating system has no way of installing additional proprietary drivers, these keyboards are not iPad compatible. Sadly, the Juno-Di and Juno-Gi require that additional Roland proprietary drivers be installed into the operating system. Any devices (keyboards, etc.) whose operating systems include these built-in 'basic' drivers will also be 'compliant' and able to communicate. In Apple-speak, this is 'CORE MIDI COMPLIANT'. In Windows-speak, this is 'FULLY CLASS COMPLIANT'.
Beginning with Windows XP Service Pack 2, and for some time, MAC OS have included built-in 'basic' MIDI drivers.
