It's been a long road, but Isis — the mobile wallet platform backed by three US carriers — is finally opening up to consumers nationwide today. After more than a year of tests in select cities, the NFC-powered technology can now be used at a variety of retailers, pharmacies, restaurants, and other locations across the US. Isis is a joint venture between Verizon Wireless, AT&T, and T-Mobile, and the carriers are hoping that their pay-with-your-phone solution will find more mainstream momentum than previous attempts at a digital wallet from Google, Square, and PayPal. It's proven to be a tough market, with consumers yet to decidedly choose a winner.

Can Isis succeed where Google Wallet failed?

But getting started with Isis isn't exactly convenient at this point. Most important, of course, is that you own a compatible Android smartphone (specific models vary by carrier). Assuming that's true, you'll also need to visit AT&T, Verizon, or T-Mobile for a special "enhanced" SIM card. This contains the necessary secure element that allows Isis to process mobile payments. Once you've met both of those criteria, all it takes is downloading the Isis Mobile Wallet app from Google Play and you'll be off and running. If you've got an American Express card or any credit card from Chase, you can use your existing card for payments. Any other debit or credit card requires funneling money into a prepaid American Express Serve account. It's not an impossibly difficult process, but requiring consumers to go out of their way to use Isis could hurt the platform's growth in the long run.

Nationwide partners include CVS, Macy's, Jamba Juice, Radio Shack, and others. Isis is also being used at select Walgreens locations, but the company isn't yet offering the payment method nationwide. (You can find a list of nearby participating businesses here.) Since Apple doesn't build NFC into its iOS products, iPhone owners are unable to use Isis. That's a problem the carriers are hoping to fix at some point, presumably with a case or some sort of accessory that could bring in Apple's massive user base.

Update: This article has been updated to clarify that Isis is only available at select Walgreens locations.