While we keep talking about Google Wallet mobile payment features, that are available only on NFC-ready devices, the fact remains that Google is not the only company out there interested in getting into the mobile payment business.

Three of the main four U.S. carriers – Verizon, AT&T and T-Mobile – have joined forces to create the ISIS venture, a mobile platform of their own that would compete directly with Google Wallet, which explains why some NFC-enabled Android handsets do not support Google Wallet on these carriers. On top of that, there are also plenty of other mobile payment initiatives out there that are just getting started.

But while interested consumers can already use Google Wallet, ISIS, and other alternatives, are yet to be rolled out as functional mobile payment systems.

However, it’s worth noting that T-Mobile has recently released a Galaxy S2 Ice Cream Sandwich update – Android 4.0.3, build version T989UVLH1 – that brings smartphone owners NFC/ISIS support in addition to some bug fixes.

The software update is available via the KIES software for PC or Mac, and it can’t be installed over-the-air (OTA). In case you have already installed it, let us know whether there are any ISIS features on board, although we highly doubt the service is already active – the three carriers would have surely made a big fuss about launching it.