Telecom provider Verizon is offering a free digital supermarket coupon service for its wireless and FiOS TV customers. Customers can obtain Verizon SpendSmart digital coupons via wireless phone, TV or computer. Verizon is providing this service through a partnership with online mobile coupon network Cellfire. The coupons can be used at more than 20 grocery chains nationwide, including ShopRite, Safeway and Kroger, with coupon brands and products rotating every two weeks.