The iPad is already well established as a "home recording" solution. There are many interface options as well as digital mics. A few of the dozen's of iPad recording Apps are:
Garage Band for iPad
Sonoma Studio Track
According to Sound Devices, the USBPre2 does work with the iPad. I have a USBPre2, but no iPad (yet), so haven't tried it.
See below (from Sound Devices):
USBPre 2 with Apple iPad
The USBPre 2 can be used as an audio input and out device with Apple’s iPad. An iPad running IOS 3.2 and 4.2 can use USB Class-Compliant audio devices, such as the USBPre 2 for audio I/O. Because the iPad does not provide full bus-powering, an external, powered hub is required.
* USBPre 2
* Apple iPad
* Apple iPad Camera Connection Kit, which includes the dock-to-USB adapter
* powered USB hub
* standard USB interconnection cord
Steps for interconnection with an iPad:
1. Connect the powered USB hub to the iPad using the Apple dock-to-USB adapter.
2. Hold down the input 1 button on the USBPre 2 and continue to hold it while connecting to the powered hub. Holding this button forces the USBPre 2 to be a USB Class 1 device (versus USB Class 2, its normal operation).
3. Verify that audio is routed to the USBPre 2.
Please note that use of external USB audio devices is an undocumented feature of the iPad and IOS.
On the other end of the scale, there is even an iPad App that allows control and metering of the Sound Devices 788t 12-track recorder.