Water spots - can you get in line water softeners

[Lovey1]

This week i noticed that my window cleaners had a water softener in the back of their van. Is there a similar (but low cost) system that is available for installing in line with the hose pipe? A metallic dark blue car with very hard water current equate to more time polishing off the water spots than actually cleaning the car!

[Lovey1]

Excellent. Exactly the solution i was looking for. thanks