I have Readdle Scanner Pro for iPhone, works good but I have heard that the iPad version only works on the New iPad (improved camera), because the iPad 2 had a crappy camera, scanning is not that great.
I had the same problem with my XGPS150, I could not pair again, so I removed the device, rebooted my iPad, and it paired again without any problems. Not sure why my iPad would not pair with the gps receiver.