The developer does not know anything about the customer except what is given in the Google Wallet payment details. That data will not be used by the developer except for accounting and tax purposes, where required by the relevant tax authorities.
Gesture Suite does not, to the best of the developer's knowledge, send any data, anywhere, unless it is requested by the user e.g. sending an automatic SMS.
Possible exception: the developer has no control over the data which Google may collect when Gesture Suite uses Google services.