This has always been the case, regardless of any Tesla involvement. This just makes the correlation between safe driving and lower cost a little less abstract.

It will be interesting to see how this develops. Will they begin selling this data? I imagine it's valuable for rental car agencies, ride-share apps, etc etc.

They probably won't sell it but i can imagine them licensing access to the real time data and then other insurers could potentially insure the driver or some similar scheme

Selling access to the data in some fashion (think how Google, FB, etc allow advertisers to buy access to a certain user to shoaw ads) as a recurring business model is probably more profitable