By now, there are various powerbanks that are designed esp. for the Apple Watch. With those & the Watch recharging pretty quickly, power should not be a real issue.
For calls (even occasionally) I would recommend AirPods, though, as the speaker in the S3 is not sufficient in loud(er) environments. Besides, you may not want to have others listening to your calls that easily (apart from the rudeness factor when doing speaker calls in public).
For calls (even occasionally) I would recommend AirPods, though, as the speaker in the S3 is not sufficient in loud(er) environments. Besides, you may not want to have others listening to your calls that easily (apart from the rudeness factor when doing speaker calls in public).