Coupons ain't dead—they're digital. And now investors have a chance to cash in on the trend.

Americans continue to love a deal, even if they do more of their shopping online. Some 103.5 million adults redeemed digital coupons last year, a 12 percent increase from 2012, according to eMarketer. Usage is expected to continue growing apace until at least 2016, when the research firm projects 124 million adults will use digital coupons.