Sat Nav on PDA

climbed out of the car and thought I’ve got one too many electric boxes to cart around so I’m (maybe) looking at SatNav/GPS software for a PDA (HP Ipaq) or SmartPhone

anyone got any good ideas, horror stories, or other thoughts?

Yes I know all you over the other side of the pond think GB isn’t LARGE enough to need a SatNav to get around, but speaking as someone who can get lost in a supermarket car park…(!!)

thanks