Providing functionality for a text to be sent after a sale, one that could include a variety of communications, would be very helpful in keeping shops and their customers connected. The first step on this could be simply a tick box at the end of the transaction at the same place that you are asked about sending an e-receipt.

Clicking "Send Text Template", could allow you to send a google/yelp review request to the customer, a simple thank you for shopping with us text, etc etc.

This could be an optional text feature, utilizing specific templates, and should be set to a workflow that only can be started at the end of each transaction in order to control text costs.