As expected, trials of Isis' NFC-based mobile payments service went live in Austin, Texas, and Salt Lake City today after its planned summer launch was delayed last month.

The program will give Isis backers Verizon Wireless, AT&T and T-Mobile USA an indication of whether the mobile wallet could be a source of revenue.

“The launch of the Isis Mobile Wallet in Austin and Salt Lake City represents a milestone for both Isis and the mobile commerce industry,” Isis chief marketing officer Ryan Hughes said.

Isis plans to generate income from promotions and advertisements running on its app, plus fees charged to financial institutions that make their cards available in the mobile wallet.

The amount of money spent worldwide through NFC mobile payments is expected to grow from $4 billion this year to $191 billion in 2017, according to a recent forecast from ABI Research. The bulk of that growth is expected to come from ticketing and transportation.

The Isis mobile wallet app is available on nine phones and is slated to launch on 11 additional models by the end of the year. The service is currently only available on NFC-capable Android smartphones.

T-Mobile lists its Isis-ready smartphones as the Samsung Galaxy S III, Galaxy S II and Galaxy S Relay 4G. By the end of the year, T-Mobile plans to expand its Isis lineup with the HTC Amaze 4G and the Samsung Galaxy Note II.

Verizon's website so far only lists one Isis phone, the HTC Droid Incredible 4G LTE. AT&T has not named its Isis-ready smartphones.

Customers must visit an operator retail store to sign up for Isis, where they'll receive a secure SIM card. They then download the Isis app from Google Play and load a compatible card from American Express, Capital One or Chase into the wallet. Isis NFC payments are accepted at "hundreds" of retail stores in the two trial markets.

Isis is promoting the service in Salt Lake City by offering customers free rides on public transportation through Jan. 13 of next year.

Logistical challenges forced Isis to push out the original launch date of the service. In an interview with Wireless Week earlier this year, marketing director Jaymee Johnson said that progress had been slowed by the complexity of both setting up back-end payment processing systems, procuring compatible smartphones and installing NFC point-of-sale systems at hundreds of retail stores.