Cleveland Clinic does this, and it's amazing. The first time I went in they gave me a little sheet of paper that had a code to sign up to their site with (myChart) and now I can get all of my test results, make appointments, and message my doctor all online.
I’ve got a few doctor’s offices/clinics that are in MyChart. It’s wildly convenient. The app and site are generally poorly designed, but work well enough that I’d rather have it than not.
The Universal Health Network of hospitals in Ontario have recently started using an online portal as well - the interface is a little intuitive but it's so much better than the alternative