Google has rolled their wallet out for several chains; I see the NFC readers in Walgreen's when I'm sent their for milk.  But Isis has been relatively quiet until now.  As of last week they have finally launched in their two test cities: Austin, and Salt Lake City.  Below are the supported carriers and phones as of now, but more phones will be added later.

• AT&T supports: HTC One™ X, LG Escape™, Samsung Galaxy Exhilarate™, Samsung Galaxy S® III, Samsung Galaxy Rugby Pro™
• T-Mobile supports: Samsung Galaxy S® II, Samsung Galaxy S® III, Samsung Galaxy S® Relay 4G
• Verizon supports: Droid Incredible 4G LTE.

Of course iPhone owners have no wallet since Apple didn't included an NFC chip.

To start using Isis, you have to take your NFC-capable phone to your carrier's store to get the SIM replaced with a more sophisticated one that has a secure element configured for Isis.  The "secure element" is the cryptographic logic that secures mobile payments.  Carriers like the secure element in the SIM while non-carriers (like Google) prefer the secure element in the phone's electronics. (I'm not entirely sure if you could support both Isis and Google Wallet on the same phone.  Anybody know?)

Then you can download the Isis app from Google Play and load your cards.  Most credit cards are supported, and there's a process to verify the credit cards are valid.  Then you can select from the list of participating retailers to "follow."  Selecting a retailer allows that retailer to give you offers via the app.

The app is well done and easy to use.  You can select a default payment type and also switch between them easily.  When the phone is tapped on the reader, there are two exchanges of information.  The payment information is transferred, and then the Isis "SmartTap" information which includes optional loyalty number and digital coupons.  Of course the value of mobile wallets comes from the ease of handling all three data types (i.e. payment, loyalty, offers).

There are several advertisements for Isis running now, and my favorite is below.