At $15k, you can afford to buy a lot of miles on congested roads before you get a GPS simulator... and you'd have to be pretty concerned about maintaining your privacy. Still, I suppose a higher demand might produce a mass-market if the government don't make it a requirement to have a license to own one of these things legally.
The major problems with road pricing that might trip it up lie elsewhere, in the unpredictability of journey cost (who'd buy a train ticket if the price, paid upon arrival, could be double or triple the lowest quoted cost, and higher if the train were delayed?) and the billing, payment and enforcement burden. Road Tax and fuel tax are standardised charges easily collectable, and whatever road pricing scheme is used, the hauliers are going to squeal, so put the congestion charge on petrol tax. but be clear about what you're doing and abandon the road tax element.
The problem with doing that in a cost-neutral way is that the hauliers don't at the moment pay their fair share, and so will get lumbered with higher costs which, if the government has the balls to make 'em stick, will increase freight costs and therefore raise inflation as they're passed on to retail prices.