Perhaps someone knows different, but AFAIK, and in my experience: The 830 will record speed, distance, power and HR using those sensors while GPS is off using the indoor activity profile. However, to follow a course or previous activity on the 830 while riding indoors, you need a "smart trainer", that is one that has controllable resistance and communicates with the 830 via ANT+. Here's the 830 manual section that describes that.
