Nelson,
These will find little use at home, unless you need or want fairly accurate radii on fillets and grooves. You would use them to find the closest radius when you round over an edge or grind a tool for same. They would also help in the latter example to show you if your curve is smooth or has flats and whibbles (technical term) in it.
They could be useful if you needed to fit the curve of a new part into an existing feature, as in a repair.
For the price, they're worth hanging onto, just in case a need comes up.