If the Sprint device can connect wirelessly using WiFi, use a NetGear WNCE2001 or Linksys WET610N wireless bridge. I have used Linksys bridge connected to Remoterig quite successfully.
On same topic, I recently added tethering to my Apple IPhone on AT&T in Florida, but found wireless tethering is not available for Iphone 3GS, only for IPhone 4. I connected Iphone to a laptop and used the ICS sharing in Windows with the Remoterig. Audio download was ok at 3Mbps, but uplink was unacceptable and audio was choppy. Need to do additional testing with Remoterig to adjust audio jitter, etc.