Right Silvervarg- the calc battery was made from material that had a 12.5yr half-life so it had some available power for close to 30 years. Thorium half life is 220+ years so available power should be around 440-550 years, which is where it becomes cost effective.
And you are also correct in that a calculator doesn't burn much power up but stratigically use of power would be happening soon enough anyway. With a thorium powered car, you would drive it and then plug it in to your work or house when you arrived.
The biggest obstical I see for the present is the cost to upfront buy the car and life-time power source . . . Which would last you a couple lifetimes of energy (if power consumption per capita does not increase).