A traditional magnetic compass can be confused by metal (ferrous) objects in the vicinity. Do you have a way of reading just what the phone's compass is saying,

A traditional magnetic compass can be confused by metal (ferrous) objects in the vicinity. Do you have a way of reading just what the phone's compass is saying, as opposed to the output of some software that uses all available information? If you do it would be interesting to check how well the compass works when the phone is in a car and attached as it would be when used for navigation.