BEWARE:

There are companies going around pretending that they have gps signals on the cables they put in your trees. This is impossible and false.

First: a cable should be 3/4 the way up your tree. It should be professional galvanized steel cable. Lags must be put in ( professional ones ) not ones that are bought at Home Depot. 

Second: they should not be spurring your live tree, this is bad and very unhealthy for the tree. Leaving it susceptible to insects and disease.

Cables are a very good prevent item to help secure a split from co dominant to dominant. It's a good way to help that split heal! They last up to 15 years!

just beware of these guys coming to your door! Consult an arborist or get a second bid/opinion