In March, Google released a major update to the Google iPhone App.
According to some reports there is a bug with the app and how it overrides the bluetooth controls of the iPhone.
A Google Mobile Help thread has confirmed reports from Google on the issue.
Googler Zeke said earlier this month:
The issue is when your phone detects a bluetooth connection, the Google app tries to connect with it – ultimately interrupting other bluetooth connections.
One person explained his frustration:
I am surprised I have not seen more complaints about this or experienced it myself – but I haven’t.
Forum discussion at Google Mobile Help.