Mobile banking isn’t limited to the mobile phone any longer.

Westpac New Zealand, a standalone company owned by Sydney, Australia-based Westpac Banking Corp., has jumped to the front of the innovation queue with a smartwatch app live in the wild.

Called Cash Tank, the software displays the user’s account balance in a clever graphic that resembles the gas tank gauge of a car (or petrol tank of an auto, depending on your lingo). The app was released about a month ago, and Westpac has made a test model available to Bank Innovation for a first-look at this first in wearable banking.

Cash Tank is built for the Sony SmartWatch, and is tethered to a slightly more sophisticated app on an Android-based phone. Bank Innovation tested by the SmartWatch and the app on a Samsung Galaxy Core smartphone, also provided by Westpac New Zealand.

Indeed, the entire SmartWatch is controlled by the Bluetooth connection to its phone. The watch itself contains limited settings and configuration options, but the important functions are dictated by the watch.

The core function of Cash Tank is the balance monitoring, and it is cool. Viewing a balance may not be the most dynamic feature imaginable, but it is clearly useful, similar to — but even easier than — GoBank’s or Bank of the West’s Slide for Balance feature on their respective mobile apps.

“Cash Tank on smartphones was used nearly 40 million times over the last year to answer the most frequently asked question in banking, ‘What’s my balance?'” said Simon Pomeroy, head of digital banking & customer experience for Westpac New Zealand. “Customers can now do at the touch of their wrist. It’s all about offering a customer led experience that’s simple, functional and really convenient and that’s connected across all interaction channels.”

As for the future of smartwatch banking, Pomeroy said, “We are now working on extending the smartwatch functionality to offer customers quick transfers between their bank accounts and the ability to receive account alerts to the watch.”

Westpac Banking as a whole is committed to mobile, as its CEO Gail Kelly indicated in an interview dated December 7 in The Australian.

“More than 40% of our customers are now interacting with us through online or mobile,” Kelly said. “We need to make that experience simple, reliable and specific to them. We believe technology plays a critical role in our relationships with our customers and our ambition is to use technology in ways that deepen those relationships.”

The possibilities for bank apps on smart watches are many. The watch could be used to display geo-sensitive alerts and offers, locate branches, and could even serve as a payment instrument. As a payment instrument, a watch is actually superior to the mobile phone. It is already out in the open and it is securely attached to one’s body.

The SmartWatch app in our test was not without some shortcomings, but most of those were related to the SmartWatch, not to Westpac New Zealand’s app. For example, the SmartWatch times out after too short an interval. It doesn’t hold a charge well, either. We wouldn’t recommend the Samsung Galaxy Core, as well. Cash Tank, meanwhile, is a great start — but only a start. Even so, just to launch a banking app for a SmartWatch deserves kudos.

Westpac New Zealand is part of the Westpac Banking Corp., which had $631 billion of assets at the end of last quarter and serves about 12 million customers.

A video of the app launching and calibrating is below.