I have been told by NI:
"With that release of NI-DAQmx Base 2.0.1 the USB-6008, 6009, and 6501 can be used with a PDA. There are some caveats to using these devices with a PDA.
1. To use a USB device, the PDA must have USB hosting capabilities as it must act as the master USB device. Currently, few PDAs have this capability.
2. Some PDAs turn off their USB port to save power if they are not active."
They have also said that PDA's supporting USB host connections "should" be ok with the USB-6008, 6009, and 6501 devices.
Cheers,
Ray.