I'm not sure the cost would be worth it for an S3.
Wireless charging is too slow. I might recommend external charger and extra batteries. That's what I did with my S3. Worked ok. Pretty cheap from Amazon - Charger and 3 batteries for less than $25, but will take a bit to get here (not Prime eligible).
http://www.amazon.ca/Neewer-2300mah-...attery+charger