I've got a Navman 3400 running on an Ipaq 3680 and it works very well - I've used the supplied vacumm sucker mount that I've stuck to the windscreen on the right side if the steering wheel.
I don't have the heated screen though. After initialisation, I generally get 5 or 6 satellite fixes whilst driving round, and 9-10 fixes standing outside.
The only thing I have seen on the web round the problem of receiving the satellite signal is to get a re-transmitter - essentially an external antenna you stick on the roof, passing the signal to a transmitter you place on the rear parcel shelf, which the Navman unit then receives.
Post your results if you proceed with Navman!
John |