I work for automotive company and we are bumping into issues with tracking a target regularly. It is different than you are trying to achieve, we usually need quite high accuracy, but this stuff might inspire you some way. Long story short - it is trouble. Big trouble.
Compass / magnetometer - those things accuracy is not great. Especially near all the metal car is made of. Except regular errors in magnitude of 10 degrees. 20 if really unlucky.
Accelerometer + gyro is much better, but you can't rely on accelerometer data holding the trajectory for too long. It diverts very soon, due to accumulation of error.
Since it is a scooter, you most likely don't have access to vehicle CAN / OBD data. In cars, reading real speed and yaw rate (how fast vehicle rotates around Z axis) gives pretty good results (if you get compensated yaw rate, but it is even longer story). Not sure how much of this gets to OBD though, we usually connect directly to CAN, where we have everything. This is serious vehicle modification though and you would need a test vehicle license plates.
In your situation, I would rely on hybrid solution, ie. sending update if any of heading, distance or time changes.
If you want great tracking accuracy though - get whatever data you can get, most likely GPS and gyro + accelerometer (I would not bother with compass, but it may be of some use - it gives you absolute heading). Then run it through Kalman filter - this is where real magic starts. You need to tune weights of different signals (ie. gyro and accelerometer will be accurate in short intervals, while GPS may jump there, but in long time GPS is much more stable, same as compass is). Kalman filter kinda averages all incoming channels into more accurate value than any of sources (if weighted well).
And if you pull this off, it might be rather different product, but it might sell great. These things tend to be rather expensive.