The ISIS Mobile Wallet app for T-Mobile customers is now available in the Google Play store. The new mobile payments service, backed by AT&T, T-Mobile, and Verizon has been expected for quite some time — it was originally slated for a September launch, but was reportedly delayed until this month. The app will only work on NFC-enabled devices on T-Mobile's network, and in line with earlier rumors, ISIS' website now lists participating retail locations in the trial markets of Salt Lake City, Utah and Austin, Texas. Those without an ISIS-ready NFC device can reportedly use an ISIS-specific SIM on certain handsets, though details of this offering remain unknown. Despite the availability of the app and the information provided on ISIS' website, neither T-Mobile nor ISIS have officially announced the start of the service's initial trial.