The answer would be yes - your store's window is a great place to your mobile call-to-action, whether it's a keyword/short code combo or a QR code. From Mobile Marketer:
“Retailers are discovering that the store is one of the best locations to present a mobile call to action,” said Stephen Burke, vice president of mobile at Resource Interactive, Columbus, OH.
“There are more mobile calls to action because there are more and more mobile assets being created by retailers,” he said.
“The good news is that that technology works and consumers are embracing mobile calls to action.”
Read more at Mobile Marketer.